lkml.org 
[lkml]   [2015]   [Jan]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.12 050/176] perf: Fix events installation during moving group
    Date
    From: Jiri Olsa <jolsa@kernel.org>

    3.12-stable review patch. If anyone has any objections, please let me know.

    ===============

    commit 9fc81d87420d0d3fd62d5e5529972c0ad9eab9cc upstream.

    We allow PMU driver to change the cpu on which the event
    should be installed to. This happened in patch:

    e2d37cd213dc ("perf: Allow the PMU driver to choose the CPU on which to install events")

    This patch also forces all the group members to follow
    the currently opened events cpu if the group happened
    to be moved.

    This and the change of event->cpu in perf_install_in_context()
    function introduced in:

    0cda4c023132 ("perf: Introduce perf_pmu_migrate_context()")

    forces group members to change their event->cpu,
    if the currently-opened-event's PMU changed the cpu
    and there is a group move.

    Above behaviour causes problem for breakpoint events,
    which uses event->cpu to touch cpu specific data for
    breakpoints accounting. By changing event->cpu, some
    breakpoints slots were wrongly accounted for given
    cpu.

    Vinces's perf fuzzer hit this issue and caused following
    WARN on my setup:

    WARNING: CPU: 0 PID: 20214 at arch/x86/kernel/hw_breakpoint.c:119 arch_install_hw_breakpoint+0x142/0x150()
    Can't find any breakpoint slot
    [...]

    This patch changes the group moving code to keep the event's
    original cpu.

    Reported-by: Vince Weaver <vince@deater.net>
    Signed-off-by: Jiri Olsa <jolsa@redhat.com>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Vince Weaver <vince@deater.net>
    Cc: Yan, Zheng <zheng.z.yan@intel.com>
    Link: http://lkml.kernel.org/r/1418243031-20367-3-git-send-email-jolsa@kernel.org
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    kernel/events/core.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index 63bd27c861fe..452b2b0d7af1 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -7167,11 +7167,11 @@ SYSCALL_DEFINE5(perf_event_open,

    if (move_group) {
    synchronize_rcu();
    - perf_install_in_context(ctx, group_leader, event->cpu);
    + perf_install_in_context(ctx, group_leader, group_leader->cpu);
    get_ctx(ctx);
    list_for_each_entry(sibling, &group_leader->sibling_list,
    group_entry) {
    - perf_install_in_context(ctx, sibling, event->cpu);
    + perf_install_in_context(ctx, sibling, sibling->cpu);
    get_ctx(ctx);
    }
    }
    --
    2.2.2


    \
     
     \ /
      Last update: 2015-01-29 11:41    [W:4.069 / U:0.576 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site