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    Subject[tip:perfcounters/core] perf_counter: fix uninitialized usage of event_list
    Commit-ID:  50d8b58c48c7acb4f4ed80c24593ffe2a9c7d1ce
    Gitweb: http://git.kernel.org/tip/50d8b58c48c7acb4f4ed80c24593ffe2a9c7d1ce
    Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
    AuthorDate: Thu, 19 Mar 2009 20:26:11 +0100
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Fri, 20 Mar 2009 11:15:11 +0100

    perf_counter: fix uninitialized usage of event_list

    Impact: fix boot crash

    When doing the generic context switch event I ran into some early
    boot hangs, which were caused by inf func recursion (event, fault,
    event, fault).

    I eventually tracked it down to event_list not being initialized
    at the time of the first event. Fix this.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    LKML-Reference: <20090319194233.195392657@chello.nl>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>


    ---
    include/linux/init_task.h | 2 ++
    kernel/perf_counter.c | 2 +-
    2 files changed, 3 insertions(+), 1 deletions(-)

    diff --git a/include/linux/init_task.h b/include/linux/init_task.h
    index 219748d..ca226a9 100644
    --- a/include/linux/init_task.h
    +++ b/include/linux/init_task.h
    @@ -124,6 +124,8 @@ extern struct cred init_cred;
    # define INIT_PERF_COUNTERS(tsk) \
    .perf_counter_ctx.counter_list = \
    LIST_HEAD_INIT(tsk.perf_counter_ctx.counter_list), \
    + .perf_counter_ctx.event_list = \
    + LIST_HEAD_INIT(tsk.perf_counter_ctx.event_list), \
    .perf_counter_ctx.lock = \
    __SPIN_LOCK_UNLOCKED(tsk.perf_counter_ctx.lock),
    #else
    diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
    index b39456a..4c4e9eb 100644
    --- a/kernel/perf_counter.c
    +++ b/kernel/perf_counter.c
    @@ -1506,7 +1506,7 @@ static void perf_swcounter_ctx_event(struct perf_counter_context *ctx,
    {
    struct perf_counter *counter;

    - if (list_empty(&ctx->event_list))
    + if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
    return;

    rcu_read_lock();

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