linux/kernel, branch v3.18

context_tracking: Restore previous state in schedule_user

2014-12-04T04:55:58Z

It appears that some SCHEDULE_USER (asm for schedule_user) callers in arch/x86/kernel/entry_64.S are called from RCU kernel context, and schedule_user will return in RCU user context. This causes RCU warnings and possible failures. This is intended to be a minimal fix suitable for 3.18. Reported-and-tested-by: Dave Jones Cc: Oleg Nesterov Cc: Frédéric Weisbecker Acked-by: Paul E. McKenney Signed-off-by: Andy Lutomirski Signed-off-by: Linus Torvalds

uprobes, x86: Fix _TIF_UPROBE vs _TIF_NOTIFY_RESUME

2014-11-23T22:25:28Z

x86 call do_notify_resume on paranoid returns if TIF_UPROBE is set but not on non-paranoid returns. I suspect that this is a mistake and that the code only works because int3 is paranoid. Setting _TIF_NOTIFY_RESUME in the uprobe code was probably a workaround for the x86 bug. With that bug fixed, we can remove _TIF_NOTIFY_RESUME from the uprobes code. Reported-by: Oleg Nesterov Acked-by: Srikar Dronamraju Acked-by: Borislav Petkov Signed-off-by: Andy Lutomirski Signed-off-by: Linus Torvalds

sched: Provide update_curr callbacks for stop/idle scheduling classes

2014-11-23T22:14:40Z

Chris bisected a NULL pointer deference in task_sched_runtime() to commit 6e998916dfe3 'sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency'. Chris observed crashes in atop or other /proc walking programs when he started fork bombs on his machine. He assumed that this is a new exit race, but that does not make any sense when looking at that commit. What's interesting is that, the commit provides update_curr callbacks for all scheduling classes except stop_task and idle_task. While nothing can ever hit that via the clock_nanosleep() and clock_gettime() interfaces, which have been the target of the commit in question, the author obviously forgot that there are other code paths which invoke task_sched_runtime() do_task_stat(() thread_group_cputime_adjusted() thread_group_cputime() task_cputime() task_sched_runtime() if (task_current(rq, p) && task_on_rq_queued(p)) { update_rq_clock(rq); up->sched_class->update_curr(rq); } If the stats are read for a stomp machine task, aka 'migration/N' and that task is current on its cpu, this will happily call the NULL pointer of stop_task->update_curr. Ooops. Chris observation that this happens faster when he runs the fork bomb makes sense as the fork bomb will kick migration threads more often so the probability to hit the issue will increase. Add the missing update_curr callbacks to the scheduler classes stop_task and idle_task. While idle tasks cannot be monitored via /proc we have other means to hit the idle case. Fixes: 6e998916dfe3 'sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency' Reported-by: Chris Mason Reported-and-tested-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: Ingo Molnar Cc: Stanislaw Gruszka Cc: Peter Zijlstra Signed-off-by: Linus Torvalds

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-11-21T23:44:54Z

Pull scheduler fixes from Ingo Molnar: "Misc fixes: two NUMA fixes, two cputime fixes and an RCU/lockdep fix" * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency sched/cputime: Fix cpu_timer_sample_group() double accounting sched/numa: Avoid selecting oneself as swap target sched/numa: Fix out of bounds read in sched_init_numa() sched: Remove lockdep check in sched_move_task()

Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-11-21T23:44:07Z

Pull perf fixes from Ingo Molnar: "Misc fixes: two Intel uncore driver fixes, a CPU-hotplug fix and a build dependencies fix" * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: perf/x86/intel/uncore: Fix boot crash on SBOX PMU on Haswell-EP perf/x86/intel/uncore: Fix IRP uncore register offsets on Haswell EP perf: Fix corruption of sibling list with hotplug perf/x86: Fix embarrasing typo

sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency

2014-11-16T09:04:20Z

Commit d670ec13178d0 "posix-cpu-timers: Cure SMP wobbles" fixes one glibc test case in cost of breaking another one. After that commit, calling clock_nanosleep(TIMER_ABSTIME, X) and then clock_gettime(&Y) can result of Y time being smaller than X time. Reproducer/tester can be found further below, it can be compiled and ran by: gcc -o tst-cpuclock2 tst-cpuclock2.c -pthread while ./tst-cpuclock2 ; do : ; done This reproducer, when running on a buggy kernel, will complain about "clock_gettime difference too small". Issue happens because on start in thread_group_cputimer() we initialize sum_exec_runtime of cputimer with threads runtime not yet accounted and then add the threads runtime to running cputimer again on scheduler tick, making it's sum_exec_runtime bigger than actual threads runtime. KOSAKI Motohiro posted a fix for this problem, but that patch was never applied: https://lkml.org/lkml/2013/5/26/191 . This patch takes different approach to cure the problem. It calls update_curr() when cputimer starts, that assure we will have updated stats of running threads and on the next schedule tick we will account only the runtime that elapsed from cputimer start. That also assure we have consistent state between cpu times of individual threads and cpu time of the process consisted by those threads. Full reproducer (tst-cpuclock2.c): #define _GNU_SOURCE #include #include #include #include #include #include #include /* Parameters for the Linux kernel ABI for CPU clocks. */ #define CPUCLOCK_SCHED 2 #define MAKE_PROCESS_CPUCLOCK(pid, clock) \ ((~(clockid_t) (pid) << 3) | (clockid_t) (clock)) static pthread_barrier_t barrier; /* Help advance the clock. */ static void *chew_cpu(void *arg) { pthread_barrier_wait(&barrier); while (1) ; return NULL; } /* Don't use the glibc wrapper. */ static int do_nanosleep(int flags, const struct timespec *req) { clockid_t clock_id = MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED); return syscall(SYS_clock_nanosleep, clock_id, flags, req, NULL); } static int64_t tsdiff(const struct timespec *before, const struct timespec *after) { int64_t before_i = before->tv_sec * 1000000000ULL + before->tv_nsec; int64_t after_i = after->tv_sec * 1000000000ULL + after->tv_nsec; return after_i - before_i; } int main(void) { int result = 0; pthread_t th; pthread_barrier_init(&barrier, NULL, 2); if (pthread_create(&th, NULL, chew_cpu, NULL) != 0) { perror("pthread_create"); return 1; } pthread_barrier_wait(&barrier); /* The test. */ struct timespec before, after, sleeptimeabs; int64_t sleepdiff, diffabs; const struct timespec sleeptime = {.tv_sec = 0,.tv_nsec = 100000000 }; /* The relative nanosleep. Not sure why this is needed, but its presence seems to make it easier to reproduce the problem. */ if (do_nanosleep(0, &sleeptime) != 0) { perror("clock_nanosleep"); return 1; } /* Get the current time. */ if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &before) < 0) { perror("clock_gettime[2]"); return 1; } /* Compute the absolute sleep time based on the current time. */ uint64_t nsec = before.tv_nsec + sleeptime.tv_nsec; sleeptimeabs.tv_sec = before.tv_sec + nsec / 1000000000; sleeptimeabs.tv_nsec = nsec % 1000000000; /* Sleep for the computed time. */ if (do_nanosleep(TIMER_ABSTIME, &sleeptimeabs) != 0) { perror("absolute clock_nanosleep"); return 1; } /* Get the time after the sleep. */ if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &after) < 0) { perror("clock_gettime[3]"); return 1; } /* The time after sleep should always be equal to or after the absolute sleep time passed to clock_nanosleep. */ sleepdiff = tsdiff(&sleeptimeabs, &after); if (sleepdiff < 0) { printf("absolute clock_nanosleep woke too early: %" PRId64 "\n", sleepdiff); result = 1; printf("Before %llu.%09llu\n", before.tv_sec, before.tv_nsec); printf("After %llu.%09llu\n", after.tv_sec, after.tv_nsec); printf("Sleep %llu.%09llu\n", sleeptimeabs.tv_sec, sleeptimeabs.tv_nsec); } /* The difference between the timestamps taken before and after the clock_nanosleep call should be equal to or more than the duration of the sleep. */ diffabs = tsdiff(&before, &after); if (diffabs < sleeptime.tv_nsec) { printf("clock_gettime difference too small: %" PRId64 "\n", diffabs); result = 1; } pthread_cancel(th); return result; } Signed-off-by: Stanislaw Gruszka Signed-off-by: Peter Zijlstra (Intel) Cc: Rik van Riel Cc: Frederic Weisbecker Cc: KOSAKI Motohiro Cc: Oleg Nesterov Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20141112155843.GA24803@redhat.com Signed-off-by: Ingo Molnar

sched/cputime: Fix cpu_timer_sample_group() double accounting

2014-11-16T09:04:18Z

While looking over the cpu-timer code I found that we appear to add the delta for the calling task twice, through: cpu_timer_sample_group() thread_group_cputimer() thread_group_cputime() times->sum_exec_runtime += task_sched_runtime(); *sample = cputime.sum_exec_runtime + task_delta_exec(); Which would make the sample run ahead, making the sleep short. Signed-off-by: Peter Zijlstra (Intel) Cc: KOSAKI Motohiro Cc: Oleg Nesterov Cc: Stanislaw Gruszka Cc: Christoph Lameter Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Rik van Riel Cc: Tejun Heo Link: http://lkml.kernel.org/r/20141112113737.GI10476@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar

sched/numa: Avoid selecting oneself as swap target

2014-11-16T09:04:17Z

Because the whole numa task selection stuff runs with preemption enabled (its long and expensive) we can end up migrating and selecting oneself as a swap target. This doesn't really work out well -- we end up trying to acquire the same lock twice for the swap migrate -- so avoid this. Reported-and-Tested-by: Sasha Levin Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20141110100328.GF29390@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar

perf: Fix corruption of sibling list with hotplug

2014-11-16T08:45:46Z

When a CPU hotplugged out, we call perf_remove_from_context() (via perf_event_exit_cpu()) to rip each CPU-bound event out of its PMU's cpu context, but leave siblings grouped together. Freeing of these events is left to the mercy of the usual refcounting. When a CPU-bound event's refcount drops to zero we cross-call to __perf_remove_from_context() to clean it up, detaching grouped siblings. This works when the relevant CPU is online, but will fail if the CPU is currently offline, and we won't detach the event from its siblings before freeing the event, leaving the sibling list corrupt. If the sibling list is later walked (e.g. because the CPU cam online again before a remaining sibling's refcount drops to zero), we will walk the now corrupted siblings list, potentially dereferencing garbage values. Given that the events should never be scheduled again (as we removed them from their context), we can simply detatch siblings when the CPU goes down in the first place. If the CPU comes back online, the redundant call to __perf_remove_from_context() is safe. Reported-by: Drew Richardson Signed-off-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Cc: vincent.weaver@maine.edu Cc: Vince Weaver Cc: Will Deacon Cc: Arnaldo Carvalho de Melo Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1415203904-25308-2-git-send-email-mark.rutland@arm.com Signed-off-by: Ingo Molnar

Merge tag 'pm+acpi-3.18-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

2014-11-14T21:38:02Z

Pull ACPI and power management fixes from Rafael Wysocki: "These are three regression fixes, two recent (generic power domains, suspend-to-idle) and one older (cpufreq), an ACPI blacklist entry for one more machine having problems with Windows 8 compatibility, a minor cpufreq driver fix (cpufreq-dt) and a fixup for new callback definitions (generic power domains). Specifics: - Fix a crash in the suspend-to-idle code path introduced by a recent commit that forgot to check a pointer against NULL before dereferencing it (Dmitry Eremin-Solenikov). - Fix a boot crash on Exynos5 introduced by a recent commit making that platform use generic Device Tree bindings for power domains which exposed a weakness in the generic power domains framework leading to that crash (Ulf Hansson). - Fix a crash during system resume on systems where cpufreq depends on Operation Performance Points (OPP) for functionality, but CONFIG_OPP is not set. This leads the cpufreq driver registration to fail, but the resume code attempts to restore the pre-suspend cpufreq configuration (which does not exist) nevertheless and crashes. From Geert Uytterhoeven. - Add a new ACPI blacklist entry for Dell Vostro 3546 that has problems if it is reported as Windows 8 compatible to the BIOS (Adam Lee). - Fix swapped arguments in an error message in the cpufreq-dt driver (Abhilash Kesavan). - Fix up the prototypes of new callbacks in struct generic_pm_domain to make them more useful. Users of those callbacks will be added in 3.19 and it's better for them to be based on the correct struct definition in mainline from the start. From Ulf Hansson and Kevin Hilman" * tag 'pm+acpi-3.18-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: PM / Domains: Fix initial default state of the need_restore flag PM / sleep: Fix entering suspend-to-IDLE if no freeze_oops is set PM / Domains: Change prototype for the attach and detach callbacks cpufreq: Avoid crash in resume on SMP without OPP cpufreq: cpufreq-dt: Fix arguments in clock failure error message ACPI / blacklist: blacklist Win8 OSI for Dell Vostro 3546