linux/include, branch v3.12.19

tty: Fix low_latency BUG

2014-05-05T12:24:38Z

commit a9c3f68f3cd8d55f809fbdb0c138ed061ea1bd25 upstream. The user-settable knob, low_latency, has been the source of several BUG reports which stem from flush_to_ldisc() running in interrupt context. Since 3.12, which added several sleeping locks (termios_rwsem and buf->lock) to the input processing path, the frequency of these BUG reports has increased. Note that changes in 3.12 did not introduce this regression; sleeping locks were first added to the input processing path with the removal of the BKL from N_TTY in commit a88a69c91256418c5907c2f1f8a0ec0a36f9e6cc, 'n_tty: Fix loss of echoed characters and remove bkl from n_tty' and later in commit 38db89799bdf11625a831c5af33938dcb11908b6, 'tty: throttling race fix'. Since those changes, executing flush_to_ldisc() in interrupt_context (ie, low_latency set), is unsafe. However, since most devices do not validate if the low_latency setting is appropriate for the context (process or interrupt) in which they receive data, some reports are due to misconfiguration. Further, serial dma devices for which dma fails, resort to interrupt receiving as a backup without resetting low_latency. Historically, low_latency was used to force wake-up the reading process rather than wait for the next scheduler tick. The effect was to trim multiple milliseconds of latency from when the process would receive new data. Recent tests [1] have shown that the reading process now receives data with only 10's of microseconds latency without low_latency set. Remove the low_latency rx steering from tty_flip_buffer_push(); however, leave the knob as an optional hint to drivers that can tune their rx fifos and such like. Cleanup stale code comments regarding low_latency. [1] https://lkml.org/lkml/2014/2/20/434 "Yay.. thats an annoying historical pain in the butt gone." -- Alan Cox Reported-by: Beat Bolli Reported-by: Pavel Roskin Acked-by: David Sterba Cc: Grant Edwards Cc: Stanislaw Gruszka Cc: Hal Murray Signed-off-by: Peter Hurley Signed-off-by: Alan Cox Signed-off-by: Jiri Slaby

bdi: avoid oops on device removal

2014-05-05T11:36:28Z

commit 5acda9d12dcf1ad0d9a5a2a7c646de3472fa7555 upstream. After commit 839a8e8660b6 ("writeback: replace custom worker pool implementation with unbound workqueue") when device is removed while we are writing to it we crash in bdi_writeback_workfn() -> set_worker_desc() because bdi->dev is NULL. This can happen because even though bdi_unregister() cancels all pending flushing work, nothing really prevents new ones from being queued from balance_dirty_pages() or other places. Fix the problem by clearing BDI_registered bit in bdi_unregister() and checking it before scheduling of any flushing work. Fixes: 839a8e8660b6777e7fe4e80af1a048aebe2b5977 Reviewed-by: Tejun Heo Signed-off-by: Jan Kara Cc: Derek Basehore Cc: Jens Axboe Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby

printk: pr_debug_ratelimited: check state first to reduce "callbacks suppressed" messages

2014-05-05T09:17:02Z

commit 29fc2bc75393864bbc9b90a7a13a0d0e11c6f41e upstream. pr_debug_ratelimited should be coded similarly to dev_dbg_ratelimited to reduce the "callbacks suppressed" messages. Add #include to printk.h. Unfortunately, this new #include must be after the prototype/declaration of function printk. It may be better to split out these _ratelimited declarations into a separate file one day. Any use of these pr__ratelimited functions must also have another specific #include . Most users have this done indirectly via #include printk.h may not #include as it causes circular dependencies and compilation failures. Signed-off-by: Joe Perches Tested-by: Krzysztof Mazur Signed-off-by: Greg Kroah-Hartman Signed-off-by: Jiri Slaby

usbnet: include wait queue head in device structure

2014-04-18T09:07:13Z

[ Upstream commit 14a0d635d18d0fb552dcc979d6d25106e6541f2e ] This fixes a race which happens by freeing an object on the stack. Quoting Julius: > The issue is > that it calls usbnet_terminate_urbs() before that, which temporarily > installs a waitqueue in dev->wait in order to be able to wait on the > tasklet to run and finish up some queues. The waiting itself looks > okay, but the access to 'dev->wait' is totally unprotected and can > race arbitrarily. I think in this case usbnet_bh() managed to succeed > it's dev->wait check just before usbnet_terminate_urbs() sets it back > to NULL. The latter then finishes and the waitqueue_t structure on its > stack gets overwritten by other functions halfway through the > wake_up() call in usbnet_bh(). The fix is to just not allocate the data structure on the stack. As dev->wait is abused as a flag it also takes a runtime PM change to fix this bug. Signed-off-by: Oliver Neukum Reported-by: Grant Grundler Tested-by: Grant Grundler Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby

tcp: syncookies: do not use getnstimeofday()

2014-04-18T09:07:07Z

[ Upstream commit 632623153196bf183a69686ed9c07eee98ff1bf8 ] While it is true that getnstimeofday() uses about 40 cycles if TSC is available, it can use 1600 cycles if hpet is the clocksource. Switch to get_jiffies_64(), as this is more than enough, and go back to 60 seconds periods. Fixes: 8c27bd75f04f ("tcp: syncookies: reduce cookie lifetime to 128 seconds") Signed-off-by: Eric Dumazet Cc: Florian Westphal Acked-by: Florian Westphal Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby

tcp: tcp_release_cb() should release socket ownership

2014-04-18T09:07:01Z

[ Upstream commit c3f9b01849ef3bc69024990092b9f42e20df7797 ] Lars Persson reported following deadlock : -000 |M:0x0:0x802B6AF8(asm) <-- arch_spin_lock -001 |tcp_v4_rcv(skb = 0x8BD527A0) <-- sk = 0x8BE6B2A0 -002 |ip_local_deliver_finish(skb = 0x8BD527A0) -003 |__netif_receive_skb_core(skb = 0x8BD527A0, ?) -004 |netif_receive_skb(skb = 0x8BD527A0) -005 |elk_poll(napi = 0x8C770500, budget = 64) -006 |net_rx_action(?) -007 |__do_softirq() -008 |do_softirq() -009 |local_bh_enable() -010 |tcp_rcv_established(sk = 0x8BE6B2A0, skb = 0x87D3A9E0, th = 0x814EBE14, ?) -011 |tcp_v4_do_rcv(sk = 0x8BE6B2A0, skb = 0x87D3A9E0) -012 |tcp_delack_timer_handler(sk = 0x8BE6B2A0) -013 |tcp_release_cb(sk = 0x8BE6B2A0) -014 |release_sock(sk = 0x8BE6B2A0) -015 |tcp_sendmsg(?, sk = 0x8BE6B2A0, ?, ?) -016 |sock_sendmsg(sock = 0x8518C4C0, msg = 0x87D8DAA8, size = 4096) -017 |kernel_sendmsg(?, ?, ?, ?, size = 4096) -018 |smb_send_kvec() -019 |smb_send_rqst(server = 0x87C4D400, rqst = 0x87D8DBA0) -020 |cifs_call_async() -021 |cifs_async_writev(wdata = 0x87FD6580) -022 |cifs_writepages(mapping = 0x852096E4, wbc = 0x87D8DC88) -023 |__writeback_single_inode(inode = 0x852095D0, wbc = 0x87D8DC88) -024 |writeback_sb_inodes(sb = 0x87D6D800, wb = 0x87E4A9C0, work = 0x87D8DD88) -025 |__writeback_inodes_wb(wb = 0x87E4A9C0, work = 0x87D8DD88) -026 |wb_writeback(wb = 0x87E4A9C0, work = 0x87D8DD88) -027 |wb_do_writeback(wb = 0x87E4A9C0, force_wait = 0) -028 |bdi_writeback_workfn(work = 0x87E4A9CC) -029 |process_one_work(worker = 0x8B045880, work = 0x87E4A9CC) -030 |worker_thread(__worker = 0x8B045880) -031 |kthread(_create = 0x87CADD90) -032 |ret_from_kernel_thread(asm) Bug occurs because __tcp_checksum_complete_user() enables BH, assuming it is running from softirq context. Lars trace involved a NIC without RX checksum support but other points are problematic as well, like the prequeue stuff. Problem is triggered by a timer, that found socket being owned by user. tcp_release_cb() should call tcp_write_timer_handler() or tcp_delack_timer_handler() in the appropriate context : BH disabled and socket lock held, but 'owned' field cleared, as if they were running from timer handlers. Fixes: 6f458dfb4092 ("tcp: improve latencies of timer triggered events") Reported-by: Lars Persson Tested-by: Lars Persson Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby

drm: add drm_set_preferred_mode

2014-04-18T09:05:05Z

commit 3cf70dafd7bbbc91df0a9ecb081d46f9f3d867f6 upstream. New helper function to set the preferred video mode. Can be called after drm_add_modes_noedid if you don't want the largest supported video mode be used by default. Signed-off-by: Gerd Hoffmann Signed-off-by: Dave Airlie Signed-off-by: Jiri Slaby

video/fb: Propagate error code from failing to unregister conflicting fb

2014-04-18T09:03:59Z

commit 46eeb2c144956e88197439b5ee5cf221a91b0a81 upstream. If we fail to remove a conflicting fb driver, we need to abort the loading of the second driver to avoid likely kernel panics. Signed-off-by: Chris Wilson Cc: Jean-Christophe Plagniol-Villard Cc: Tomi Valkeinen Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Reviewed-by: Jani Nikula Signed-off-by: Dave Airlie Signed-off-by: Jiri Slaby

floppy: bail out in open() if drive is not responding to block0 read

2014-04-18T08:58:54Z

commit 7b7b68bba5ef23734c35ffb0d8d82079ed604d33 upstream. In case reading of block 0 during open() fails, it is not the right thing to let open() succeed. Fix this by introducing FD_OPEN_SHOULD_FAIL_BIT flag, and setting it in case the bio callback encounters an error while trying to read block 0. As a bonus, this works around certain broken userspace (blkid), which is not able to properly handle read()s returning IO errors. Hence be nice to those, and bail out during open() already; if block 0 is not readable, read()s are not going to provide any meaningful data anyway. Signed-off-by: Jiri Kosina Signed-off-by: Jiri Slaby

futex: Allow architectures to skip futex_atomic_cmpxchg_inatomic() test

2014-04-13T14:40:26Z

commit 03b8c7b623c80af264c4c8d6111e5c6289933666 upstream. If an architecture has futex_atomic_cmpxchg_inatomic() implemented and there is no runtime check necessary, allow to skip the test within futex_init(). This allows to get rid of some code which would always give the same result, and also allows the compiler to optimize a couple of if statements away. Signed-off-by: Heiko Carstens Cc: Finn Thain Cc: Geert Uytterhoeven Link: http://lkml.kernel.org/r/20140302120947.GA3641@osiris Signed-off-by: Thomas Gleixner [geert: Backported to v3.10..v3.13] Signed-off-by: Geert Uytterhoeven Signed-off-by: Jiri Slaby