Commit 8550d7cb authored Jan 19, 2011 by Oleg Nesterov Committed by Ingo Molnar Jan 19, 2011

perf: Fix perf_event_init_task()/perf_event_free_task() interaction



perf_event_init_task() should clear child->perf_event_ctxp[]
before anything else. Otherwise, if
perf_event_init_context(perf_hw_context) fails,
perf_event_free_task() can free perf_event_ctxp[perf_sw_context]
copied from parent->perf_event_ctxp[] by dup_task_struct().

Also move the initialization of perf_event_mutex and
perf_event_list from perf_event_init_context() to
perf_event_init_context().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
LKML-Reference: <20110119182228.GC12183@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent dbe08d82

kernel/perf_event.c

+4 −5

Original line number	Diff line number	Diff line
		@@ -6446,11 +6446,6 @@ int perf_event_init_context(struct task_struct *child, int ctxn)
		unsigned long flags;
		int ret = 0;

		child->perf_event_ctxp[ctxn] = NULL;

		mutex_init(&child->perf_event_mutex);
		INIT_LIST_HEAD(&child->perf_event_list);

		if (likely(!parent->perf_event_ctxp[ctxn]))
		return 0;

		@@ -6539,6 +6534,10 @@ int perf_event_init_task(struct task_struct *child)
		{
		int ctxn, ret;

		memset(child->perf_event_ctxp, 0, sizeof(child->perf_event_ctxp));
		mutex_init(&child->perf_event_mutex);
		INIT_LIST_HEAD(&child->perf_event_list);

		for_each_task_context_nr(ctxn) {
		ret = perf_event_init_context(child, ctxn);
		if (ret)