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Commit 22c1558e authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: fix the output lock 



Use -1 instead of 0 as unlocked, since 0 is a valid cpu number.

( This is not an issue right now but will be once we allow multiple
  counters to output to the same mmap area. )

[ Impact: prepare code for multi-counter profile output ]

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090505155437.232686598@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c5078f78

kernel/perf_counter.c

+4 −3
Original line number Diff line number Diff line
@@ -1409,6 +1409,7 @@ static int perf_mmap_data_alloc(struct perf_counter *counter, int nr_pages) 
	}



	data->nr_pages = nr_pages;

	atomic_set(&data->lock, -1);



	rcu_assign_pointer(counter->data, data);
@@ -1755,7 +1756,7 @@ static void perf_output_lock(struct perf_output_handle *handle) 
	if (in_nmi() && atomic_read(&data->lock) == cpu)

		return;



	while (atomic_cmpxchg(&data->lock, 0, cpu) != 0)

	while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)

		cpu_relax();



	handle->locked = 1;
@@ -1784,7 +1785,7 @@ static void perf_output_unlock(struct perf_output_handle *handle) 
	 * NMI can happen here, which means we can miss a done_head update.

	 */



	cpu = atomic_xchg(&data->lock, 0);

	cpu = atomic_xchg(&data->lock, -1);

	WARN_ON_ONCE(cpu != smp_processor_id());



	/*
@@ -1794,7 +1795,7 @@ static void perf_output_unlock(struct perf_output_handle *handle) 
		/*

		 * Since we had it locked, we can lock it again.

		 */

		while (atomic_cmpxchg(&data->lock, 0, cpu) != 0)

		while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)

			cpu_relax();



		goto again;