1. 11 Jun, 2014 3 commits
    • Jiri Olsa's avatar
      perf: Prevent false warning in perf_swevent_add · 26616604
      Jiri Olsa authored
      commit 39af6b16 upstream.
      
      The perf cpu offline callback takes down all cpu context
      events and releases swhash->swevent_hlist.
      
      This could race with task context software event being just
      scheduled on this cpu via perf_swevent_add while cpu hotplug
      code already cleaned up event's data.
      
      The race happens in the gap between the cpu notifier code
      and the cpu being actually taken down. Note that only cpu
      ctx events are terminated in the perf cpu hotplug code.
      
      It's easily reproduced with:
        $ perf record -e faults perf bench sched pipe
      
      while putting one of the cpus offline:
        # echo 0 > /sys/devices/system/cpu/cpu1/online
      
      Console emits following warning:
        WARNING: CPU: 1 PID: 2845 at kernel/events/core.c:5672 perf_swevent_add+0x18d/0x1a0()
        Modules linked in:
        CPU: 1 PID: 2845 Comm: sched-pipe Tainted: G        W    3.14.0+ #256
        Hardware name: Intel Corporation Montevina platform/To be filled by O.E.M., BIOS AMVACRB1.86C.0066.B00.0805070703 05/07/2008
         0000000000000009 ffff880077233ab8 ffffffff81665a23 0000000000200005
         0000000000000000 ffff880077233af8 ffffffff8104732c 0000000000000046
         ffff88007467c800 0000000000000002 ffff88007a9cf2a0 0000000000000001
        Call Trace:
         [<ffffffff81665a23>] dump_stack+0x4f/0x7c
         [<ffffffff8104732c>] warn_slowpath_common+0x8c/0xc0
         [<ffffffff8104737a>] warn_slowpath_null+0x1a/0x20
         [<ffffffff8110fb3d>] perf_swevent_add+0x18d/0x1a0
         [<ffffffff811162ae>] event_sched_in.isra.75+0x9e/0x1f0
         [<ffffffff8111646a>] group_sched_in+0x6a/0x1f0
         [<ffffffff81083dd5>] ? sched_clock_local+0x25/0xa0
         [<ffffffff811167e6>] ctx_sched_in+0x1f6/0x450
         [<ffffffff8111757b>] perf_event_sched_in+0x6b/0xa0
         [<ffffffff81117a4b>] perf_event_context_sched_in+0x7b/0xc0
         [<ffffffff81117ece>] __perf_event_task_sched_in+0x43e/0x460
         [<ffffffff81096f1e>] ? put_lock_stats.isra.18+0xe/0x30
         [<ffffffff8107b3c8>] finish_task_switch+0xb8/0x100
         [<ffffffff8166a7de>] __schedule+0x30e/0xad0
         [<ffffffff81172dd2>] ? pipe_read+0x3e2/0x560
         [<ffffffff8166b45e>] ? preempt_schedule_irq+0x3e/0x70
         [<ffffffff8166b45e>] ? preempt_schedule_irq+0x3e/0x70
         [<ffffffff8166b464>] preempt_schedule_irq+0x44/0x70
         [<ffffffff816707f0>] retint_kernel+0x20/0x30
         [<ffffffff8109e60a>] ? lockdep_sys_exit+0x1a/0x90
         [<ffffffff812a4234>] lockdep_sys_exit_thunk+0x35/0x67
         [<ffffffff81679321>] ? sysret_check+0x5/0x56
      
      Fixing this by tracking the cpu hotplug state and displaying
      the WARN only if current cpu is initialized properly.
      
      Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
      Signed-off-by: default avatarJiri Olsa <jolsa@redhat.com>
      Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Link: http://lkml.kernel.org/r/1396861448-10097-1-git-send-email-jolsa@redhat.comSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      26616604
    • Thomas Gleixner's avatar
      sched: Sanitize irq accounting madness · ecaf19a7
      Thomas Gleixner authored
      commit 2d513868 upstream.
      
      Russell reported, that irqtime_account_idle_ticks() takes ages due to:
      
             for (i = 0; i < ticks; i++)
                     irqtime_account_process_tick(current, 0, rq);
      
      It's sad, that this code was written way _AFTER_ the NOHZ idle
      functionality was available. I charge myself guitly for not paying
      attention when that crap got merged with commit abb74cef ("sched:
      Export ns irqtimes through /proc/stat")
      
      So instead of looping nr_ticks times just apply the whole thing at
      once.
      
      As a side note: The whole cputime_t vs. u64 business in that context
      wants to be cleaned up as well. There is no point in having all these
      back and forth conversions. Lets standardise on u64 nsec for all
      kernel internal accounting and be done with it. Everything else does
      not make sense at all for fine grained accounting. Frederic, can you
      please take care of that?
      Reported-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Cc: Venkatesh Pallipadi <venki@google.com>
      Cc: Shaun Ruffell <sruffell@digium.com>
      Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1405022307000.6261@ionos.tec.linutronix.deSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      ecaf19a7
    • Steven Rostedt (Red Hat)'s avatar
      sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check · e58d78f9
      Steven Rostedt (Red Hat) authored
      commit 6227cb00 upstream.
      
      The check at the beginning of cpupri_find() makes sure that the task_pri
      variable does not exceed the cp->pri_to_cpu array length. But that length
      is CPUPRI_NR_PRIORITIES not MAX_RT_PRIO, where it will miss the last two
      priorities in that array.
      
      As task_pri is computed from convert_prio() which should never be bigger
      than CPUPRI_NR_PRIORITIES, if the check should cause a panic if it is
      hit.
      Reported-by: default avatarMike Galbraith <umgwanakikbuti@gmail.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Link: http://lkml.kernel.org/r/1397015410.5212.13.camel@marge.simpson.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      e58d78f9
  2. 07 Jun, 2014 37 commits