1. 11 Jun, 2014 2 commits
    • Jiri Olsa's avatar
      perf: Prevent false warning in perf_swevent_add · 0d41f602
      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>
      0d41f602
    • Steven Rostedt (Red Hat)'s avatar
      sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check · 4e0d105c
      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>
      4e0d105c
  2. 07 Jun, 2014 38 commits