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Subject[PATCH 3/7] perf_counter: sanitize context locking
Ensure we're consistent with the context locks.

context->mutex
context->lock
list_{add,del}_counter();
so that either lock is sufficient to stabilize the context.

LKML-Reference: <new-submission>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/perf_counter.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -597,6 +597,8 @@ static void add_counter_to_ctx(struct pe

/*
* Cross CPU call to install and enable a performance counter
+ *
+ * Must be called with ctx->mutex held
*/
static void __perf_install_in_context(void *info)
{
@@ -1496,13 +1498,13 @@ static void perf_counter_for_each_siblin
struct perf_counter_context *ctx = counter->ctx;
struct perf_counter *sibling;

- spin_lock_irq(&ctx->lock);
+ mutex_lock(&ctx->mutex);
counter = counter->group_leader;

func(counter);
list_for_each_entry(sibling, &counter->sibling_list, list_entry)
func(sibling);
- spin_unlock_irq(&ctx->lock);
+ mutex_unlock(&ctx->mutex);
}

static void perf_counter_for_each_child(struct perf_counter *counter,
@@ -3414,7 +3416,10 @@ __perf_counter_exit_task(struct task_str
struct perf_counter *parent_counter;

update_counter_times(child_counter);
+
+ spin_lock_irq(&child_ctx->lock);
list_del_counter(child_counter, child_ctx);
+ spin_unlock_irq(&child_ctx->lock);

parent_counter = child_counter->parent;
/*
--



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