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2012-05-11ARM: 7398/1: l2x0: only write to debug registers on PL310Will Deacon
commit ab4d536890853ab6675ede65db40e2c0980cb0ea upstream. PL310 errata #588369 and #727915 require writes to the debug registers of the cache controller to work around known problems. Writing these registers on L220 may cause deadlock, so ensure that we only perform this operation when we identify a PL310 at probe time. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11ARM: 7397/1: l2x0: only apply workaround for erratum #753970 on PL310Will Deacon
commit f154fe9b806574437b47f08e924ad10c0e240b23 upstream. The workaround for PL310 erratum #753970 can lead to deadlock on systems with an L220 cache controller. This patch makes the workaround effective only when the cache controller is identified as a PL310 at probe time. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11ARM: 7396/1: errata: only handle ARM erratum #326103 on affected coresWill Deacon
commit f0c4b8d653f5ee091fb8d4d02ed7eaad397491bb upstream. Erratum #326103 ("FSR write bit incorrect on a SWP to read-only memory") only affects the ARM 1136 core prior to r1p0. The workaround disassembles the faulting instruction to determine whether it was a read or write access on all v6 cores. An issue has been reported on the ARM 11MPCore whereby loading the faulting instruction may happen in parallel with that page being unmapped, resulting in a deadlock due to the lack of TLB broadcasting in hardware: http://lists.infradead.org/pipermail/linux-arm-kernel/2012-March/091561.html This patch limits the workaround so that it is only used on affected cores, which are known to be UP only. Other v6 cores can rely on the FSR to indicate the access type correctly. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11autofs: make the autofsv5 packet file descriptor use a packetized pipeLinus Torvalds
commit 64f371bc3107e69efce563a3d0f0e6880de0d537 upstream. The autofs packet size has had a very unfortunate size problem on x86: because the alignment of 'u64' differs in 32-bit and 64-bit modes, and because the packet data was not 8-byte aligned, the size of the autofsv5 packet structure differed between 32-bit and 64-bit modes despite looking otherwise identical (300 vs 304 bytes respectively). We first fixed that up by making the 64-bit compat mode know about this problem in commit a32744d4abae ("autofs: work around unhappy compat problem on x86-64"), and that made a 32-bit 'systemd' work happily on a 64-bit kernel because everything then worked the same way as on a 32-bit kernel. But it turned out that 'automount' had actually known and worked around this problem in user space, so fixing the kernel to do the proper 32-bit compatibility handling actually *broke* 32-bit automount on a 64-bit kernel, because it knew that the packet sizes were wrong and expected those incorrect sizes. As a result, we ended up reverting that compatibility mode fix, and thus breaking systemd again, in commit fcbf94b9dedd. With both automount and systemd doing a single read() system call, and verifying that they get *exactly* the size they expect but using different sizes, it seemed that fixing one of them inevitably seemed to break the other. At one point, a patch I seriously considered applying from Michael Tokarev did a "strcmp()" to see if it was automount that was doing the operation. Ugly, ugly. However, a prettier solution exists now thanks to the packetized pipe mode. By marking the communication pipe as being packetized (by simply setting the O_DIRECT flag), we can always just write the bigger packet size, and if user-space does a smaller read, it will just get that partial end result and the extra alignment padding will simply be thrown away. This makes both automount and systemd happy, since they now get the size they asked for, and the kernel side of autofs simply no longer needs to care - it could pad out the packet arbitrarily. Of course, if there is some *other* user of autofs (please, please, please tell me it ain't so - and we haven't heard of any) that tries to read the packets with multiple writes, that other user will now be broken - the whole point of the packetized mode is that one system call gets exactly one packet, and you cannot read a packet in pieces. Tested-by: Michael Tokarev <mjt@tls.msk.ru> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: David Miller <davem@davemloft.net> Cc: Ian Kent <raven@themaw.net> Cc: Thomas Meyer <thomas@m3y3r.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11pipes: add a "packetized pipe" mode for writingLinus Torvalds
commit 9883035ae7edef3ec62ad215611cb8e17d6a1a5d upstream. The actual internal pipe implementation is already really about individual packets (called "pipe buffers"), and this simply exposes that as a special packetized mode. When we are in the packetized mode (marked by O_DIRECT as suggested by Alan Cox), a write() on a pipe will not merge the new data with previous writes, so each write will get a pipe buffer of its own. The pipe buffer is then marked with the PIPE_BUF_FLAG_PACKET flag, which in turn will tell the reader side to break the read at that boundary (and throw away any partial packet contents that do not fit in the read buffer). End result: as long as you do writes less than PIPE_BUF in size (so that the pipe doesn't have to split them up), you can now treat the pipe as a packet interface, where each read() system call will read one packet at a time. You can just use a sufficiently big read buffer (PIPE_BUF is sufficient, since bigger than that doesn't guarantee atomicity anyway), and the return value of the read() will naturally give you the size of the packet. NOTE! We do not support zero-sized packets, and zero-sized reads and writes to a pipe continue to be no-ops. Also note that big packets will currently be split at write time, but that the size at which that happens is not really specified (except that it's bigger than PIPE_BUF). Currently that limit is the system page size, but we might want to explicitly support bigger packets some day. The main user for this is going to be the autofs packet interface, allowing us to stop having to care so deeply about exact packet sizes (which have had bugs with 32/64-bit compatibility modes). But user space can create packetized pipes with "pipe2(fd, O_DIRECT)", which will fail with an EINVAL on kernels that do not support this interface. Tested-by: Michael Tokarev <mjt@tls.msk.ru> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: David Miller <davem@davemloft.net> Cc: Ian Kent <raven@themaw.net> Cc: Thomas Meyer <thomas@m3y3r.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11usb gadget: uvc: uvc_request_data::length field must be signedLaurent Pinchart
commit 6f6543f53f9ce136e01d7114bf6f0818ca54fb41 upstream. The field is used to pass the UVC request data length, but can also be used to signal an error when setting it to a negative value. Switch from unsigned int to __s32. Reported-by: Fernandez Gonzalo <gfernandez@copreci.es> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11usb: gadget: dummy: do not call pullup() on udc_stop()Felipe Balbi
commit 15b120d67019d691e4389372967332d74a80522a upstream. pullup() is already called properly by udc-core.c and there's no need to call it from udc_stop(), in fact that will cause issues. Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Felipe Balbi <balbi@ti.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11USB: gadget: storage gadgets send wrong error code for unknown commandsAlan Stern
commit c85dcdac5852295cf6822f5c4331a6ddab72581f upstream. This patch (as1539) fixes a minor bug in the mass-storage gadget drivers. When an unknown command is received, the error code sent back is "Invalid Field in CDB" rather than "Invalid Command". This is because the bitmask of CDB bytes allowed to be nonzero is incorrect. When handling an unknown command, we don't care which command bytes are nonzero. All the bits in the mask should be set, not just eight of them. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: <Michal Nazarewicz <mina86@mina86.com> Signed-off-by: Felipe Balbi <balbi@ti.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11USB: EHCI: fix crash during suspend on ASUS computersAlan Stern
commit 151b61284776be2d6f02d48c23c3625678960b97 upstream. This patch (as1545) fixes a problem affecting several ASUS computers: The machine crashes or corrupts memory when going into suspend if the ehci-hcd driver is bound to any controllers. Users have been forced to unbind or unload ehci-hcd before putting their systems to sleep. After extensive testing, it was determined that the machines don't like going into suspend when any EHCI controllers are in the PCI D3 power state. Presumably this is a firmware bug, but there's nothing we can do about it except to avoid putting the controllers in D3 during system sleep. The patch adds a new flag to indicate whether the problem is present, and avoids changing the controller's power state if the flag is set. Runtime suspend is unaffected; this matters only for system suspend. However as a side effect, the controller will not respond to remote wakeup requests while the system is asleep. Hence USB wakeup is not functional -- but of course, this is already true in the current state of affairs. This fixes Bugzilla #42728. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Tested-by: Steven Rostedt <rostedt@goodmis.org> Tested-by: Andrey Rahmatullin <wrar@wrar.name> Tested-by: Oleksij Rempel (fishor) <bug-track@fisher-privat.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11USB: cdc-wdm: fix race leading leading to memory corruptionOliver Neukum
commit 5c22837adca7c30b66121cf18ad3e160134268d4 upstream. This patch fixes a race whereby a pointer to a buffer would be overwritten while the buffer was in use leading to a double free and a memory leak. This causes crashes. This bug was introduced in 2.6.34 Signed-off-by: Oliver Neukum <oneukum@suse.de> Tested-by: Bjørn Mork <bjorn@mork.no> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11ALSA: HDA: Add external mic quirk for Asus Zenbook UX31EDavid Henningsson
commit 5ac57550f279c3d991ef0b398681bcaca18169f7 upstream. According to the reporter, external mic starts to work if the laptop-dmic model is used. According to BIOS pin config, all pins are consistent with the alc269vb_laptop_dmic fixup, except for the external mic, which is not present. BugLink: https://bugs.launchpad.net/bugs/950490 Signed-off-by: David Henningsson <david.henningsson@canonical.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11nl80211: ensure interface is up in various APIsJohannes Berg
commit 2b5f8b0b44e17e625cfba1e7b88db44f4dcc0441 upstream. [backported by Ben Greear] The nl80211 handling code should ensure as much as it can that the interface is in a valid state, it can certainly ensure the interface is running. Not doing so can cause calls through mac80211 into the driver that result in warnings and unspecified behaviour in the driver. Reported-by: Ben Greear <greearb@candelatech.com> Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: Ben Greear <greearb@candelatech.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11drm/i915: fix integer overflow in i915_gem_do_execbuffer()Xi Wang
commit 44afb3a04391a74309d16180d1e4f8386fdfa745 upstream. On 32-bit systems, a large args->num_cliprects from userspace via ioctl may overflow the allocation size, leading to out-of-bounds access. This vulnerability was introduced in commit 432e58ed ("drm/i915: Avoid allocation for execbuffer object list"). Signed-off-by: Xi Wang <xi.wang@gmail.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11drm/i915: fix integer overflow in i915_gem_execbuffer2()Xi Wang
commit ed8cd3b2cd61004cab85380c52b1817aca1ca49b upstream. On 32-bit systems, a large args->buffer_count from userspace via ioctl may overflow the allocation size, leading to out-of-bounds access. This vulnerability was introduced in commit 8408c282 ("drm/i915: First try a normal large kmalloc for the temporary exec buffers"). Signed-off-by: Xi Wang <xi.wang@gmail.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11drm/i915: Set the Stencil Cache eviction policy to non-LRA mode.Kenneth Graunke
commit 3a69ddd6f872180b6f61fda87152b37202118fbc upstream. Clearing bit 5 of CACHE_MODE_0 is necessary to prevent GPU hangs in OpenGL programs such as Google MapsGL, Google Earth, and gzdoom when using separate stencil buffers. Without it, the GPU tries to use the LRA eviction policy, which isn't supported. This was supposed to be off by default, but seems to be on for many machines. This cannot be done in gen6_init_clock_gating with most of the other workaround bits; the render ring needs to exist. Otherwise, the register write gets dropped on the floor (one printk will show it changed, but a second printk immediately following shows the value reverts to the old one). Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=47535 Cc: Rob Castle <futuredub@gmail.com> Cc: Eric Appleman <erappleman@gmail.com> Cc: aaron667@gmx.net Cc: Keith Packard <keithp@keithp.com> Signed-off-by: Kenneth Graunke <kenneth@whitecape.org> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Dave Airlie <airlied@redhat.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11drm/i915: Force sync command ordering (Gen6+)Ben Widawsky
commit 84f9f938be4156e4baea466688bd6abae1c9e6ba upstream. The docs say this is required for Gen7, and since the bit was added for Gen6, we are also setting it there pit pf paranoia. Particularly as Chris points out, if PIPE_CONTROL counts as a 3d state packet. This was found through doc inspection by Ken and applies to Gen6+; Reported-by: Kenneth Graunke <kenneth@whitecape.org> Signed-off-by: Ben Widawsky <ben@bwidawsk.net> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Reviewed-by: Eric Anholt <eric@anholt.net> Signed-off-by: Keith Packard <keithp@keithp.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11drm/i915: relative_constants_mode race fixBen Widawsky
commit e2971bdab2b761683353da383c0fd5ac704d1cca upstream. dev_priv keeps track of the current addressing mode that gets set at execbuffer time. Unfortunately the existing code was doing this before acquiring struct_mutex which leaves a race with another thread also doing an execbuffer. If that wasn't bad enough, relocate_slow drops struct_mutex which opens a much more likely error where another thread comes in and modifies the state while relocate_slow is being slow. The solution here is to just defer setting this state until we absolutely need it, and we know we'll have struct_mutex for the remainder of our code path. v2: Keith noticed a bug in the original patch. Signed-off-by: Ben Widawsky <ben@bwidawsk.net> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Keith Packard <keithp@keithp.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11drm/i915: handle input/output sdvo timings separately in mode_setDaniel Vetter
commit 6651819b4b4fc3caa6964c5d825eb4bb996f3905 upstream. We seem to have a decent confusion between the output timings and the input timings of the sdvo encoder. If I understand the code correctly, we use the original mode unchanged for the output timings, safe for the lvds case. And we should use the adjusted mode for input timings. Clarify the situation by adding an explicit output_dtd to the sdvo mode_set function and streamline the code-flow by moving the input and output mode setting in the sdvo encode together. Furthermore testing showed that the sdvo input timing needs the unadjusted dotclock, the sdvo chip will automatically compute the required pixel multiplier to get a dotclock above 100 MHz. Fix this up when converting a drm mode to an sdvo dtd. This regression was introduced in commit c74696b9c890074c1e1ee3d7496fc71eb3680ced Author: Pavel Roskin <proski@gnu.org> Date: Thu Sep 2 14:46:34 2010 -0400 i915: revert some checks added by commit 32aad86f particularly the following hunk: > diff --git a/drivers/gpu/drm/i915/intel_sdvo.c > b/drivers/gpu/drm/i915/intel_sdvo.c > index 093e914..62d22ae 100644 > --- a/drivers/gpu/drm/i915/intel_sdvo.c > +++ b/drivers/gpu/drm/i915/intel_sdvo.c > @@ -1122,11 +1123,9 @@ static void intel_sdvo_mode_set(struct drm_encoder *encoder, > > /* We have tried to get input timing in mode_fixup, and filled into > adjusted_mode */ > - if (intel_sdvo->is_tv || intel_sdvo->is_lvds) { > - intel_sdvo_get_dtd_from_mode(&input_dtd, adjusted_mode); > + intel_sdvo_get_dtd_from_mode(&input_dtd, adjusted_mode); > + if (intel_sdvo->is_tv || intel_sdvo->is_lvds) > input_dtd.part2.sdvo_flags = intel_sdvo->sdvo_flags; > - } else > - intel_sdvo_get_dtd_from_mode(&input_dtd, mode); > > /* If it's a TV, we already set the output timing in mode_fixup. > * Otherwise, the output timing is equal to the input timing. Due to questions raised in review, below a more elaborate analysis of the bug at hand: Sdvo seems to have two timings, one is the output timing which will be sent over whatever is connected on the other side of the sdvo chip (panel, hdmi screen, tv), the other is the input timing which will be generated by the gmch pipe. It looks like sdvo is expected to scale between the two. To make things slightly more complicated, we have a bunch of special cases: - For lvds panel we always use a fixed output timing, namely intel_sdvo->sdvo_lvds_fixed_mode, hence that special case. - Sdvo has an interface to generate a preferred input timing for a given output timing. This is the confusing thing that I've tried to clear up with the follow-on patches. - A special requirement is that the input pixel clock needs to be between 100MHz and 200MHz (likely to keep it within the electromechanical design range of PCIe), 270MHz on later gen4+. Lower pixel clocks are doubled/quadrupled. The thing this patch tries to fix is that the pipe needs to be explicitly instructed to double/quadruple the pixels and needs the correspondingly higher pixel clock, whereas the sdvo adaptor seems to do that itself and needs the unadjusted pixel clock. For the sdvo encode side we already set the pixel mutliplier with a different command (0x21). This patch tries to fix this mess by: - Keeping the output mode timing in the unadjusted plain mode, safe for the lvds case. - Storing the input timing in the adjusted_mode with the adjusted pixel clock. This way we don't need to frob around with the core crtc mode set code. - Fixing up the pixelclock when constructing the sdvo dtd timing struct. This is why the first hunk of the patch is an integral part of the series. - Dropping the is_tv special case because input_dtd is equivalent to adjusted_mode after these changes. Follow-up patches clear this up further (by simply ripping out intel_sdvo->input_dtd because it's not needed). v2: Extend commit message with an in-depth bug analysis. Reported-and-Tested-by: Bernard Blackham <b-linuxgit@largestprime.net> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=48157 Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> [bwh: Indented the hunk quoted above so quilt doesn't try to apply it] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11drm/radeon/kms: need to set up ss on DP bridges as wellAlex Deucher
commit 700698e7c303f5095107c62a81872c2c3dad1702 upstream. Makes Nutmeg DP to VGA bridges work for me. Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=42490 Noticed by Jerome Glisse (after weeks of debugging). Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Signed-off-by: Dave Airlie <airlied@redhat.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11dell-laptop: Terminate quirks list properlyMartin Nyhus
commit d62d421b071b08249361044d8e56c8b5c3ed6aa7 upstream. Add missing DMI_NONE entry to end of the quirks list so dmi_check_system() won't read past the end of the list. Signed-off-by: Martin Nyhus <martin.nyhus@gmx.com> Signed-off-by: Matthew Garrett <mjg@redhat.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11hwmon: (fam15h_power) Fix pci_device_id arrayGuenter Roeck
commit c3e40a9972428d6e2d8e287ed0233a57a218c30f upstream. pci_match_id() takes an *array* of IDs which must be properly zero- terminated. Reported-by: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com> Acked-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11hwmon: fam15h_power: fix bogus values with current BIOSesAndre Przywara
commit 00250ec90963b7ef6678438888f3244985ecde14 upstream. Newer BKDG[1] versions recommend a different initialization value for the running average range register in the northbridge. This improves the power reading by avoiding counter saturations resulting in bogus values for anything below about 80% of TDP power consumption. Updated BIOSes will have this new value set up from the beginning, but meanwhile we correct this value ourselves. This needs to be done on all northbridges, even on those where the driver itself does not register at. This fixes the driver on all current machines to provide proper values for idle load. [1] http://support.amd.com/us/Processor_TechDocs/42301_15h_Mod_00h-0Fh_BKDG.pdf Chapter 3.8: D18F5xE0 Processor TDP Running Average (p. 452) Signed-off-by: Andre Przywara <andre.przywara@amd.com> Acked-by: Jean Delvare <khali@linux-fr.org> [guenter.roeck@ericsson.com: Removed unnecessary return statement] Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11tracing: Fix stacktrace of latency tracers (irqsoff and friends)Steven Rostedt
commit db4c75cbebd7e5910cd3bcb6790272fcc3042857 upstream. While debugging a latency with someone on IRC (mirage335) on #linux-rt (OFTC), we discovered that the stacktrace output of the latency tracers (preemptirqsoff) was empty. This bug was caused by the creation of the dynamic length stack trace again (like commit 12b5da3 "tracing: Fix ent_size in trace output" was). This bug is caused by the latency tracers requiring the next event to determine the time between the current event and the next. But by grabbing the next event, the iter->ent_size is set to the next event instead of the current one. As the stacktrace event is the last event, this makes the ent_size zero and causes nothing to be printed for the stack trace. The dynamic stacktrace uses the ent_size to determine how much of the stack can be printed. The ent_size of zero means no stack. The simple fix is to save the iter->ent_size before finding the next event. Note, mirage335 asked to remain anonymous from LKML and git, so I will not add the Reported-by and Tested-by tags, even though he did report the issue and tested the fix. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11sched: Fix OOPS when build_sched_domains() percpu allocation failshe, bo
commit fb2cf2c660971bea0ad86a9a5c19ad39eab61344 upstream. Under extreme memory used up situations, percpu allocation might fail. We hit it when system goes to suspend-to-ram, causing a kworker panic: EIP: [<c124411a>] build_sched_domains+0x23a/0xad0 Kernel panic - not syncing: Fatal exception Pid: 3026, comm: kworker/u:3 3.0.8-137473-gf42fbef #1 Call Trace: [<c18cc4f2>] panic+0x66/0x16c [...] [<c1244c37>] partition_sched_domains+0x287/0x4b0 [<c12a77be>] cpuset_update_active_cpus+0x1fe/0x210 [<c123712d>] cpuset_cpu_inactive+0x1d/0x30 [...] With this fix applied build_sched_domains() will return -ENOMEM and the suspend attempt fails. Signed-off-by: he, bo <bo.he@intel.com> Reviewed-by: Zhang, Yanmin <yanmin.zhang@intel.com> Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1335355161.5892.17.camel@hebo [ So, we fail to deallocate a CPU because we cannot allocate RAM :-/ I don't like that kind of sad behavior but nevertheless it should not crash under high memory load. ] Signed-off-by: Ingo Molnar <mingo@kernel.org> [bwh: Backported to 3.2: change filename] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11dmaengine: at_hdmac: remove clear-on-read in atc_dostart()Nicolas Ferre
commit ed8b0d67f33518a16c6b2450fe5ebebf180c2d04 upstream. This loop on EBCISR register was designed to clear IRQ sources before enabling a DMA channel. This register is clear-on-read so a race condition can appear if another channel is already active and has just finished its transfer. Removing this read on EBCISR is fixing the issue as there is no case where an IRQ could be pending: we already make sure that this register is drained at probe() time and during resume. Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com> Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11ASoC: wm8994: Improve sequencing of AIF channel enablesMark Brown
commit 1a38336b8611a04f0a624330c1f815421f4bf5f4 upstream. This ensures a clean startup of the channels, without this change some use cases could result in issues in a small proportion of cases. Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11ASoC: dapm: Ensure power gets managed for line widgetsMark Brown
commit 7e1f7c8a6e517900cd84da1b8ae020f08f286c3b upstream. Line widgets had not been included in either the power up or power down sequences so if a widget had an event associated with it that event would never be run. Fix this minimally by adding them to the sequences, we should probably be doing away with the specific widget types as they all have the same priority anyway. Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11xen/smp: Fix crash when booting with ACPI hotplug CPUs.Konrad Rzeszutek Wilk
commit cf405ae612b0f7e2358db7ff594c0e94846137aa upstream. When we boot on a machine that can hotplug CPUs and we are using 'dom0_max_vcpus=X' on the Xen hypervisor line to clip the amount of CPUs available to the initial domain, we get this: (XEN) Command line: com1=115200,8n1 dom0_mem=8G noreboot dom0_max_vcpus=8 sync_console mce_verbosity=verbose console=com1,vga loglvl=all guest_loglvl=all .. snip.. DMI: Intel Corporation S2600CP/S2600CP, BIOS SE5C600.86B.99.99.x032.072520111118 07/25/2011 .. snip. SMP: Allowing 64 CPUs, 32 hotplug CPUs installing Xen timer for CPU 7 cpu 7 spinlock event irq 361 NMI watchdog: disabled (cpu7): hardware events not enabled Brought up 8 CPUs .. snip.. [acpi processor finds the CPUs are not initialized and starts calling arch_register_cpu, which creates /sys/devices/system/cpu/cpu8/online] CPU 8 got hotplugged CPU 9 got hotplugged CPU 10 got hotplugged .. snip.. initcall 1_acpi_battery_init_async+0x0/0x1b returned 0 after 406 usecs calling erst_init+0x0/0x2bb @ 1 [and the scheduler sticks newly started tasks on the new CPUs, but said CPUs cannot be initialized b/c the hypervisor has limited the amount of vCPUS to 8 - as per the dom0_max_vcpus=8 flag. The spinlock tries to kick the other CPU, but the structure for that is not initialized and we crash.] BUG: unable to handle kernel paging request at fffffffffffffed8 IP: [<ffffffff81035289>] xen_spin_lock+0x29/0x60 PGD 180d067 PUD 180e067 PMD 0 Oops: 0002 [#1] SMP CPU 7 Modules linked in: Pid: 1, comm: swapper/0 Not tainted 3.4.0-rc2upstream-00001-gf5154e8 #1 Intel Corporation S2600CP/S2600CP RIP: e030:[<ffffffff81035289>] [<ffffffff81035289>] xen_spin_lock+0x29/0x60 RSP: e02b:ffff8801fb9b3a70 EFLAGS: 00010282 With this patch, we cap the amount of vCPUS that the initial domain can run, to exactly what dom0_max_vcpus=X has specified. In the future, if there is a hypercall that will allow a running domain to expand past its initial set of vCPUS, this patch should be re-evaluated. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11xen: correctly check for pending events when restoring irq flagsDavid Vrabel
commit 7eb7ce4d2e8991aff4ecb71a81949a907ca755ac upstream. In xen_restore_fl_direct(), xen_force_evtchn_callback() was being called even if no events were pending. This resulted in (depending on workload) about a 100 times as many xen_version hypercalls as necessary. Fix this by correcting the sense of the conditional jump. This seems to give a significant performance benefit for some workloads. There is some subtle tricksy "..since the check here is trying to check both pending and masked in a single cmpw, but I think this is correct. It will call check_events now only when the combined mask+pending word is 0x0001 (aka unmasked, pending)." (Ian) Acked-by: Ian Campbell <ian.campbell@citrix.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11Revert "autofs: work around unhappy compat problem on x86-64"Linus Torvalds
commit fcbf94b9dedd2ce08e798a99aafc94fec8668161 upstream. This reverts commit a32744d4abae24572eff7269bc17895c41bd0085. While that commit was technically the right thing to do, and made the x86-64 compat mode work identically to native 32-bit mode (and thus fixing the problem with a 32-bit systemd install on a 64-bit kernel), it turns out that the automount binaries had workarounds for this compat problem. Now, the workarounds are disgusting: doing an "uname()" to find out the architecture of the kernel, and then comparing it for the 64-bit cases and fixing up the size of the read() in automount for those. And they were confused: it's not actually a generic 64-bit issue at all, it's very much tied to just x86-64, which has different alignment for an 'u64' in 64-bit mode than in 32-bit mode. But the end result is that fixing the compat layer actually breaks the case of a 32-bit automount on a x86-64 kernel. There are various approaches to fix this (including just doing a "strcmp()" on current->comm and comparing it to "automount"), but I think that I will do the one that teaches pipes about a special "packet mode", which will allow user space to not have to care too deeply about the padding at the end of the autofs packet. That change will make the compat workaround unnecessary, so let's revert it first, and get automount working again in compat mode. The packetized pipes will then fix autofs for systemd. Reported-and-requested-by: Michael Tokarev <mjt@tls.msk.ru> Cc: Ian Kent <raven@themaw.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11x86, apic: APIC code touches invalid MSR on P5 class machinesBryan O'Donoghue
commit cbf2829b61c136edcba302a5e1b6b40e97d32c00 upstream. Current APIC code assumes MSR_IA32_APICBASE is present for all systems. Pentium Classic P5 and friends didn't have this MSR. MSR_IA32_APICBASE was introduced as an architectural MSR by Intel @ P6. Code paths that can touch this MSR invalidly are when vendor == Intel && cpu-family == 5 and APIC bit is set in CPUID - or when you simply pass lapic on the kernel command line, on a P5. The below patch stops Linux incorrectly interfering with the MSR_IA32_APICBASE for P5 class machines. Other code paths exist that touch the MSR - however those paths are not currently reachable for a conformant P5. Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linux.intel.com> Link: http://lkml.kernel.org/r/4F8EEDD3.1080404@linux.intel.com Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11x86, microcode: Fix sysfs warning during module unload on unsupported CPUsAndreas Herrmann
commit a956bd6f8583326b18348ab1452b4686778f785d upstream. Loading the microcode driver on an unsupported CPU and subsequently unloading the driver causes WARNING: at fs/sysfs/group.c:138 mc_device_remove+0x5f/0x70 [microcode]() Hardware name: 01972NG sysfs group ffffffffa00013d0 not found for kobject 'cpu0' Modules linked in: snd_hda_codec_hdmi snd_hda_codec_conexant snd_hda_intel btusb snd_hda_codec bluetooth thinkpad_acpi rfkill microcode(-) [last unloaded: cfg80211] Pid: 4560, comm: modprobe Not tainted 3.4.0-rc2-00002-g258f742 #5 Call Trace: [<ffffffff8103113b>] ? warn_slowpath_common+0x7b/0xc0 [<ffffffff81031235>] ? warn_slowpath_fmt+0x45/0x50 [<ffffffff81120e74>] ? sysfs_remove_group+0x34/0x120 [<ffffffffa00000ef>] ? mc_device_remove+0x5f/0x70 [microcode] [<ffffffff81331eb9>] ? subsys_interface_unregister+0x69/0xa0 [<ffffffff81563526>] ? mutex_lock+0x16/0x40 [<ffffffffa0000c3e>] ? microcode_exit+0x50/0x92 [microcode] [<ffffffff8107051d>] ? sys_delete_module+0x16d/0x260 [<ffffffff810a0065>] ? wait_iff_congested+0x45/0x110 [<ffffffff815656af>] ? page_fault+0x1f/0x30 [<ffffffff81565ba2>] ? system_call_fastpath+0x16/0x1b on recent kernels. This is due to commit 8a25a2fd126c ("cpu: convert 'cpu' and 'machinecheck' sysdev_class to a regular subsystem") which renders commit 6c53cbfced04 ("x86, microcode: Correct sysdev_add error path") useless. See http://marc.info/?l=linux-kernel&m=133416246406478 Avoid above warning by restoring the old driver behaviour before 6c53cbfced04 ("x86, microcode: Correct sysdev_add error path"). Cc: Tigran Aivazian <tigran@aivazian.fsnet.co.uk> Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Link: http://lkml.kernel.org/r/20120411163849.GE4794@alberich.amd.com Signed-off-by: Borislav Petkov <borislav.petkov@amd.com> [bwh: Backported to 3.2: deleted line uses sys_dev, not dev] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11NFS: put open context on error in nfs_flush_multiFred Isaman
commit 8ccd271f7a3a846ce6f85ead0760d9d12994a611 upstream. Signed-off-by: Fred Isaman <iisaman@netapp.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11NFS: put open context on error in nfs_pagein_multiFred Isaman
commit 73fb7bc7c57d971b11f2e00536ac2d3e316e0609 upstream. Signed-off-by: Fred Isaman <iisaman@netapp.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11NFSv4: Ensure that we check lock exclusive/shared type against open modesTrond Myklebust
commit 55725513b5ef9d462aa3e18527658a0362aaae83 upstream. Since we may be simulating flock() locks using NFS byte range locks, we can't rely on the VFS having checked the file open mode for us. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11NFSv4: Ensure that the LOCK code sets exception->inodeTrond Myklebust
commit 05ffe24f5290dc095f98fbaf84afe51ef404ccc5 upstream. All callers of nfs4_handle_exception() that need to handle NFS4ERR_OPENMODE correctly should set exception->inode Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11nfs: Enclose hostname in brackets when needed in nfs_do_root_mountJan Kara
commit 98a2139f4f4d7b5fcc3a54c7fddbe88612abed20 upstream. When hostname contains colon (e.g. when it is an IPv6 address) it needs to be enclosed in brackets to make parsing of NFS device string possible. Fix nfs_do_root_mount() to enclose hostname properly when needed. NFS code actually does not need this as it does not parse the string passed by nfs_do_root_mount() but the device string is exposed to userspace in /proc/mounts. CC: Josh Boyer <jwboyer@redhat.com> CC: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11tcp: fix TCP_MAXSEG for established IPv6 passive socketsNeal Cardwell
[ Upstream commit d135c522f1234f62e81be29cebdf59e9955139ad ] Commit f5fff5d forgot to fix TCP_MAXSEG behavior IPv6 sockets, so IPv6 TCP server sockets that used TCP_MAXSEG would find that the advmss of child sockets would be incorrect. This commit mirrors the advmss logic from tcp_v4_syn_recv_sock in tcp_v6_syn_recv_sock. Eventually this logic should probably be shared between IPv4 and IPv6, but this at least fixes this issue. Signed-off-by: Neal Cardwell <ncardwell@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11net ax25: Reorder ax25_exit to remove races.Eric W. Biederman
[ Upstream commit 3adadc08cc1e2cbcc15a640d639297ef5fcb17f5 ] While reviewing the sysctl code in ax25 I spotted races in ax25_exit where it is possible to receive notifications and packets after already freeing up some of the data structures needed to process those notifications and updates. Call unregister_netdevice_notifier early so that the rest of the cleanup code does not need to deal with network devices. This takes advantage of my recent enhancement to unregister_netdevice_notifier to send unregister notifications of all network devices that are current registered. Move the unregistration for packet types, socket types and protocol types before we cleanup any of the ax25 data structures to remove the possibilities of other races. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11ksz884x: don't copy too much in netdev_set_mac_address()Dan Carpenter
[ Upstream commit 716af4abd6e6370226f567af50bfaca274515980 ] MAX_ADDR_LEN is 32. ETH_ALEN is 6. mac->sa_data is a 14 byte array, so the memcpy() is doing a read past the end of the array. I asked about this on netdev and Ben Hutchings told me it's supposed to be copying ETH_ALEN bytes (thanks Ben). Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11netns: do not leak net_generic data on failed initJulian Anastasov
[ Upstream commit b922934d017f1cc831b017913ed7d1a56c558b43 ] ops_init should free the net_generic data on init failure and __register_pernet_operations should not call ops_free when NET_NS is not enabled. Signed-off-by: Julian Anastasov <ja@ssi.bg> Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11tcp: fix tcp_grow_window() for large incoming framesEric Dumazet
[ Upstream commit 4d846f02392a710f9604892ac3329e628e60a230 ] tcp_grow_window() has to grow rcv_ssthresh up to window_clamp, allowing sender to increase its window. tcp_grow_window() still assumes a tcp frame is under MSS, but its no longer true with LRO/GRO. This patch fixes one of the performance issue we noticed with GRO on. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Neal Cardwell <ncardwell@google.com> Cc: Tom Herbert <therbert@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11dummy: Add ndo_uninit().Hiroaki SHIMODA
commit 890fdf2a0cb88202d1427589db2cf29c1bdd3c1d upstream. In register_netdevice(), when ndo_init() is successful and later some error occurred, ndo_uninit() will be called. So dummy deivce is desirable to implement ndo_uninit() method to free percpu stats for this case. And, ndo_uninit() is also called along with dev->destructor() when device is unregistered, so in order to prevent dev->dstats from being freed twice, dev->destructor is modified to free_netdev(). Signed-off-by: Hiroaki SHIMODA <shimoda.hiroaki@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11net: usb: smsc75xx: fix mtuStephane Fillod
[ Upstream commit a99ff7d0123b19ecad3b589480b6542716ab6b52 ] Make smsc75xx recalculate the hard_mtu after adjusting the hard_header_len. Without this, usbnet adjusts the MTU down to 1492 bytes, and the host is unable to receive standard 1500-byte frames from the device. Inspired by same fix on cdc_eem 78fb72f7936c01d5b426c03a691eca082b03f2b9. Tested on ARM/Omap3 with EVB-LAN7500-LC. Signed-off-by: Stephane Fillod <fillods@users.sf.net> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11net_sched: gred: Fix oops in gred_dump() in WRED modeDavid Ward
[ Upstream commit 244b65dbfede788f2fa3fe2463c44d0809e97c6b ] A parameter set exists for WRED mode, called wred_set, to hold the same values for qavg and qidlestart across all VQs. The WRED mode values had been previously held in the VQ for the default DP. After these values were moved to wred_set, the VQ for the default DP was no longer created automatically (so that it could be omitted on purpose, to have packets in the default DP enqueued directly to the device without using RED). However, gred_dump() was overlooked during that change; in WRED mode it still reads qavg/qidlestart from the VQ for the default DP, which might not even exist. As a result, this command sequence will cause an oops: tc qdisc add dev $DEV handle $HANDLE parent $PARENT gred setup \ DPs 3 default 2 grio tc qdisc change dev $DEV handle $HANDLE gred DP 0 prio 8 $RED_OPTIONS tc qdisc change dev $DEV handle $HANDLE gred DP 1 prio 8 $RED_OPTIONS This fixes gred_dump() in WRED mode to use the values held in wred_set. Signed-off-by: David Ward <david.ward@ll.mit.edu> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11net/ethernet: ks8851_mll fix rx frame buffer overflowDavide Ciminaghi
[ Upstream commit 8a9a0ea6032186e3030419262678d652b88bf6a8 ] At the beginning of ks_rcv(), a for loop retrieves the header information relevant to all the frames stored in the mac's internal buffers. The number of pending frames is stored as an 8 bits field in KS_RXFCTR. If interrupts are disabled long enough to allow for more than 32 frames to accumulate in the MAC's internal buffers, a buffer overflow occurs. This patch fixes the problem by making the driver's frame_head_info buffer big enough. Well actually, since the chip appears to have 12K of internal rx buffers and the shortest ethernet frame should be 64 bytes long, maybe the limit could be set to 12*1024/64 = 192 frames, but 255 should be safer. Signed-off-by: Davide Ciminaghi <ciminaghi@gnudd.com> Signed-off-by: Raffaele Recalcati <raffaele.recalcati@bticino.it> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11net: smsc911x: fix skb handling in receive pathWill Deacon
[ Upstream commit 3c5e979bd037888dd7d722da22da4b43659af485 ] The SMSC911x driver resets the ->head, ->data and ->tail pointers in the skb on the reset path in order to avoid buffer overflow due to packet padding performed by the hardware. This patch fixes the receive path so that the skb pointers are fixed up after the data has been read from the device, The error path is also fixed to use number of words consistently and prevent erroneous FIFO fastforwarding when skipping over bad data. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-118139cp: set intr mask after its handler is registeredJason Wang
[ Upstream commit a8c9cb106fe79c28d6b7f1397652cadd228715ff ] We set intr mask before its handler is registered, this does not work well when 8139cp is sharing irq line with other devices. As the irq could be enabled by the device before 8139cp's hander is registered which may lead unhandled irq. Fix this by introducing an helper cp_irq_enable() and call it after request_irq(). Signed-off-by: Jason Wang <jasowang@redhat.com> Reviewed-by: Flavio Leitner <fbl@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11atl1: fix kernel panic in case of DMA errorsTony Zelenoff
[ Upstream commit 03662e41c7cff64a776bfb1b3816de4be43de881 ] Problem: There was two separate work_struct structures which share one handler. Unfortunately getting atl1_adapter structure from work_struct in case of DMA error was done from incorrect offset which cause kernel panics. Solution: The useless work_struct for DMA error removed and handler name changed to more generic one. Signed-off-by: Tony Zelenoff <antonz@parallels.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
2012-05-11tcp: avoid order-1 allocations on wifi and tx pathEric Dumazet
[ This combines upstream commit a21d45726acacc963d8baddf74607d9b74e2b723 and the follow-on bug fix commit 22b4a4f22da4b39c6f7f679fd35f3d35c91bf851 ] Marc Merlin reported many order-1 allocations failures in TX path on its wireless setup, that dont make any sense with MTU=1500 network, and non SG capable hardware. After investigation, it turns out TCP uses sk_stream_alloc_skb() and used as a convention skb_tailroom(skb) to know how many bytes of data payload could be put in this