linux/kernel, branch v2.6.32.42

time: Compensate for rounding on odd-frequency clocksources

2011-06-23T22:24:09Z

commit a386b5af8edda1c742ce9f77891e112eefffc005 upstream. When the clocksource is not a multiple of HZ, the clock will be off. For acpi_pm, HZ=1000 the error is 127.111 ppm: The rounding of cycle_interval ends up generating a false error term in ntp_error accumulation since xtime_interval is not exactly 1/HZ. So, we subtract out the error caused by the rounding. This has been visible since 2.6.32-rc2 commit a092ff0f90cae22b2ac8028ecd2c6f6c1a9e4601 time: Implement logarithmic time accumulation That commit raised NTP_INTERVAL_FREQ and exposed the rounding error. testing tool: http://n1.taur.dk/permanent/testpmt.c Also tested with ntpd and a frequency counter. Signed-off-by: Kasper Pedersen Acked-by: john stultz Cc: John Kacur Cc: Clark Williams Cc: Martin Schwidefsky Signed-off-by: Andrew Morton Signed-off-by: Thomas Gleixner Signed-off-by: Will Tisdale Signed-off-by: Greg Kroah-Hartman

genirq: Add IRQF_FORCE_RESUME

2011-06-23T22:24:09Z

commit dc5f219e88294b93009eef946251251ffffb6d60 upstream. Xen needs to reenable interrupts which are marked IRQF_NO_SUSPEND in the resume path. Add a flag to force the reenabling in the resume code. Tested-and-acked-by: Ian Campbell Signed-off-by: Thomas Gleixner Signed-off-by: Stefan Bader Signed-off-by: Greg Kroah-Hartman

lockdep: Fix lock_is_held() on recursion

2011-06-23T22:24:06Z

commit f2513cde93f0957d5dc6c09bc24b0cccd27d8e1d upstream. The main lock_is_held() user is lockdep_assert_held(), avoid false assertions in lockdep_off() sections by unconditionally reporting the lock is taken. [ the reason this is important is a lockdep_assert_held() in ttwu() which triggers a warning under lockdep_off() as in printk() which can trigger another wakeup and lock up due to spinlock recursion, as reported and heroically debugged by Arne Jansen ] Reported-and-tested-by: Arne Jansen Signed-off-by: Peter Zijlstra Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1307398759.2497.966.camel@laptop Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

ftrace: Only update the function code on write to filter files

2011-06-23T22:24:00Z

commit 058e297d34a404caaa5ed277de15698d8dc43000 upstream. If function tracing is enabled, a read of the filter files will cause the call to stop_machine to update the function trace sites. It should only call stop_machine on write. Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

tick: Clear broadcast active bit when switching to oneshot

2011-05-23T18:20:19Z

commit 07f4beb0b5bbfaf36a64aa00d59e670ec578a95a upstream. The first cpu which switches from periodic to oneshot mode switches also the broadcast device into oneshot mode. The broadcast device serves as a backup for per cpu timers which stop in deeper C-states. To avoid starvation of the cpus which might be in idle and depend on broadcast mode it marks the other cpus as broadcast active and sets the brodcast expiry value of those cpus to the next tick. The oneshot mode broadcast bit for the other cpus is sticky and gets only cleared when those cpus exit idle. If a cpu was not idle while the bit got set in consequence the bit prevents that the broadcast device is armed on behalf of that cpu when it enters idle for the first time after it switched to oneshot mode. In most cases that goes unnoticed as one of the other cpus has usually a timer pending which keeps the broadcast device armed with a short timeout. Now if the only cpu which has a short timer active has the bit set then the broadcast device will not be armed on behalf of that cpu and will fire way after the expected timer expiry. In the case of Christians bug report it took ~145 seconds which is about half of the wrap around time of HPET (the limit for that device) due to the fact that all other cpus had no timers armed which expired before the 145 seconds timeframe. The solution is simply to clear the broadcast active bit unconditionally when a cpu switches to oneshot mode after the first cpu switched the broadcast device over. It's not idle at that point otherwise it would not be executing that code. [ I fundamentally hate that broadcast crap. Why the heck thought some folks that when going into deep idle it's a brilliant concept to switch off the last device which brings the cpu back from that state? ] Thanks to Christian for providing all the valuable debug information! Reported-and-tested-by: Christian Hoffmann Cc: John Stultz Link: http://lkml.kernel.org/r/%3Calpine.LFD.2.02.1105161105170.3078%40ionos%3E Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

clocksource: Install completely before selecting

2011-05-23T18:20:19Z

commit e05b2efb82596905ebfe88e8612ee81dec9b6592 upstream. Christian Hoffmann reported that the command line clocksource override with acpi_pm timer fails: Kernel command line: clocksource=acpi_pm hpet clockevent registered Switching to clocksource hpet Override clocksource acpi_pm is not HRT compatible. Cannot switch while in HRT/NOHZ mode. The watchdog code is what enables CLOCK_SOURCE_VALID_FOR_HRES, but we actually end up selecting the clocksource before we enqueue it into the watchdog list, so that's why we see the warning and fail to switch to acpi_pm timer as requested. That's particularly bad when we want to debug timekeeping related problems in early boot. Put the selection call last. Reported-by: Christian Hoffmann Signed-off-by: John Stultz Link: http://lkml.kernel.org/r/%3C1304558210.2943.24.camel%40work-vm%3E Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

Fix time() inconsistencies caused by intermediate xtime_cache values being read

2011-05-23T18:20:15Z

Currently with 2.6.32-longterm, its possible for time() to occasionally return values one second earlier then the previous time() call. This happens because update_xtime_cache() does: xtime_cache = xtime; timespec_add_ns(&xtime_cache, nsec); Its possible that xtime is 1sec,999msecs, and nsecs is 1ms, resulting in a xtime_cache that is 2sec,0ms. get_seconds() (which is used by sys_time()) does not take the xtime_lock, which is ok as the xtime.tv_sec value is a long and can be atomically read safely. The problem occurs the next call to update_xtime_cache() if xtime has not increased: /* This sets xtime_cache back to 1sec, 999msec */ xtime_cache = xtime; /* get_seconds, calls here, and sees a 1second inconsistency */ timespec_add_ns(&xtime_cache, nsec); In order to resolve this, we could add locking to get_seconds(), but it needs to be lock free, as it is called from the machine check handler, opening a possible deadlock. So instead, this patch introduces an intermediate value for the calculations, so that we only assign xtime_cache once with the correct time, using ACCESS_ONCE to make sure the compiler doesn't optimize out any intermediate values. The xtime_cache manipulations were removed with 2.6.35, so that kernel and later do not need this change. In 2.6.33 and 2.6.34 the logarithmic accumulation should make it so xtime is updated each tick, so it is unlikely that two updates to xtime_cache could occur while the difference between xtime and xtime_cache crosses the second boundary. However, the paranoid might want to pull this into 2.6.33/34-longterm just to be sure. Thanks to Stephen for helping finally narrow down the root cause and many hours of help with testing and validation. Also thanks to Max, Andi, Eric and Paul for review of earlier attempts and helping clarify what is possible with regard to out of order execution. Acked-by: Eric Dumazet Signed-off-by: John Stultz Signed-off-by: Greg Kroah-Hartman

next_pidmap: fix overflow condition

2011-04-22T15:44:25Z

commit c78193e9c7bcbf25b8237ad0dec82f805c4ea69b upstream. next_pidmap() just quietly accepted whatever 'last' pid that was passed in, which is not all that safe when one of the users is /proc. Admittedly the proc code should do some sanity checking on the range (and that will be the next commit), but that doesn't mean that the helper functions should just do that pidmap pointer arithmetic without checking the range of its arguments. So clamp 'last' to PID_MAX_LIMIT. The fact that we then do "last+1" doesn't really matter, the for-loop does check against the end of the pidmap array properly (it's only the actual pointer arithmetic overflow case we need to worry about, and going one bit beyond isn't going to overflow). [ Use PID_MAX_LIMIT rather than pid_max as per Eric Biederman ] Reported-by: Tavis Ormandy Analyzed-by: Robert Święcki Cc: Eric W. Biederman Cc: Pavel Emelyanov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

repair gdbstub to match the gdbserial protocol specification

2011-04-14T23:53:40Z

commit fb82c0ff27b2c40c6f7a3d1a94cafb154591fa80 upstream. The gdbserial protocol handler should return an empty packet instead of an error string when ever it responds to a command it does not implement. The problem cases come from a debugger client sending qTBuffer, qTStatus, qSearch, qSupported. The incorrect response from the gdbstub leads the debugger clients to not function correctly. Recent versions of gdb will not detach correctly as a result of this behavior. Backport-request-by: Frank Pan Signed-off-by: Jason Wessel Signed-off-by: Dongdong Deng Signed-off-by: Greg Kroah-Hartman

Relax si_code check in rt_sigqueueinfo and rt_tgsigqueueinfo

2011-04-14T23:53:24Z

commit 243b422af9ea9af4ead07a8ad54c90d4f9b6081a upstream. Commit da48524eb206 ("Prevent rt_sigqueueinfo and rt_tgsigqueueinfo from spoofing the signal code") made the check on si_code too strict. There are several legitimate places where glibc wants to queue a negative si_code different from SI_QUEUE: - This was first noticed with glibc's aio implementation, which wants to queue a signal with si_code SI_ASYNCIO; the current kernel causes glibc's tst-aio4 test to fail because rt_sigqueueinfo() fails with EPERM. - Further examination of the glibc source shows that getaddrinfo_a() wants to use SI_ASYNCNL (which the kernel does not even define). The timer_create() fallback code wants to queue signals with SI_TIMER. As suggested by Oleg Nesterov , loosen the check to forbid only the problematic SI_TKILL case. Reported-by: Klaus Dittrich Acked-by: Julien Tinnes Signed-off-by: Roland Dreier Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman