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Commit 8bc20959 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: Fix inheritance cleanup code 



Clean up code that open-coded the list_{add,del}_counter() code in
__perf_counter_exit_task() which consequently diverged. This could
lead to software counter crashes.

Also, fold the ctx->nr_counter inc/dec into those functions and clean
up some of the related code.

[ Impact: fix potential sw counter crash, cleanup ]

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 0bbd0d4b

kernel/perf_counter.c

+15 −17
Original line number Diff line number Diff line
@@ -115,6 +115,7 @@ list_add_counter(struct perf_counter *counter, struct perf_counter_context *ctx) 
	}



	list_add_rcu(&counter->event_entry, &ctx->event_list);

	ctx->nr_counters++;

}



static void
@@ -122,6 +123,8 @@ list_del_counter(struct perf_counter *counter, struct perf_counter_context *ctx) 
{

	struct perf_counter *sibling, *tmp;



	ctx->nr_counters--;



	list_del_init(&counter->list_entry);

	list_del_rcu(&counter->event_entry);
@@ -209,7 +212,6 @@ static void __perf_counter_remove_from_context(void *info) 
	counter_sched_out(counter, cpuctx, ctx);



	counter->task = NULL;

	ctx->nr_counters--;



	/*

	 * Protect the list operation against NMI by disabling the
@@ -276,7 +278,6 @@ retry: 
	 * succeed.

	 */

	if (!list_empty(&counter->list_entry)) {

		ctx->nr_counters--;

		list_del_counter(counter, ctx);

		counter->task = NULL;

	}
@@ -544,7 +545,6 @@ static void add_counter_to_ctx(struct perf_counter *counter, 
			       struct perf_counter_context *ctx)

{

	list_add_counter(counter, ctx);

	ctx->nr_counters++;

	counter->prev_state = PERF_COUNTER_STATE_OFF;

	counter->tstamp_enabled = ctx->time;

	counter->tstamp_running = ctx->time;
@@ -3206,9 +3206,8 @@ static int inherit_group(struct perf_counter *parent_counter, 
static void sync_child_counter(struct perf_counter *child_counter,

			       struct perf_counter *parent_counter)

{

	u64 parent_val, child_val;

	u64 child_val;



	parent_val = atomic64_read(&parent_counter->count);

	child_val = atomic64_read(&child_counter->count);



	/*
@@ -3240,7 +3239,6 @@ __perf_counter_exit_task(struct task_struct *child, 
			 struct perf_counter_context *child_ctx)

{

	struct perf_counter *parent_counter;

	struct perf_counter *sub, *tmp;



	/*

	 * If we do not self-reap then we have to wait for the
@@ -3252,8 +3250,8 @@ __perf_counter_exit_task(struct task_struct *child, 
	 */

	if (child != current) {

		wait_task_inactive(child, 0);

		list_del_init(&child_counter->list_entry);

		update_counter_times(child_counter);

		list_del_counter(child_counter, child_ctx);

	} else {

		struct perf_cpu_context *cpuctx;

		unsigned long flags;
@@ -3272,9 +3270,7 @@ __perf_counter_exit_task(struct task_struct *child, 
		group_sched_out(child_counter, cpuctx, child_ctx);

		update_counter_times(child_counter);



		list_del_init(&child_counter->list_entry);



		child_ctx->nr_counters--;

		list_del_counter(child_counter, child_ctx);



		perf_enable();

		local_irq_restore(flags);
@@ -3288,13 +3284,6 @@ __perf_counter_exit_task(struct task_struct *child, 
	 */

	if (parent_counter) {

		sync_child_counter(child_counter, parent_counter);

		list_for_each_entry_safe(sub, tmp, &child_counter->sibling_list,

					 list_entry) {

			if (sub->parent) {

				sync_child_counter(sub, sub->parent);

				free_counter(sub);

			}

		}

		free_counter(child_counter);

	}

}
@@ -3315,9 +3304,18 @@ void perf_counter_exit_task(struct task_struct *child) 
	if (likely(!child_ctx->nr_counters))

		return;



again:

	list_for_each_entry_safe(child_counter, tmp, &child_ctx->counter_list,

				 list_entry)

		__perf_counter_exit_task(child, child_counter, child_ctx);



	/*

	 * If the last counter was a group counter, it will have appended all

	 * its siblings to the list, but we obtained 'tmp' before that which

	 * will still point to the list head terminating the iteration.

	 */

	if (!list_empty(&child_ctx->counter_list))

		goto again;

}



/*