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Commit efe951d3 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf/x86: Fix perf,x86,cpuhp deadlock 



More lockdep gifts, a 5-way lockup race:

	perf_event_create_kernel_counter()
	  perf_event_alloc()
	    perf_try_init_event()
	      x86_pmu_event_init()
		__x86_pmu_event_init()
		  x86_reserve_hardware()
 #0		    mutex_lock(&pmc_reserve_mutex);
		    reserve_ds_buffer()
 #1		      get_online_cpus()

	perf_event_release_kernel()
	  _free_event()
	    hw_perf_event_destroy()
	      x86_release_hardware()
 #0		mutex_lock(&pmc_reserve_mutex)
		release_ds_buffer()
 #1		  get_online_cpus()

 #1	do_cpu_up()
	  perf_event_init_cpu()
 #2	    mutex_lock(&pmus_lock)
 #3	    mutex_lock(&ctx->mutex)

	sys_perf_event_open()
	  mutex_lock_double()
 #3	    mutex_lock(ctx->mutex)
 #4	    mutex_lock_nested(ctx->mutex, 1);

	perf_try_init_event()
 #4	  mutex_lock_nested(ctx->mutex, 1)
	  x86_pmu_event_init()
	    intel_pmu_hw_config()
	      x86_add_exclusive()
 #0		mutex_lock(&pmc_reserve_mutex)

Fix it by using ordering constructs instead of locking.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0c7296ca

arch/x86/events/intel/ds.c

+18 −15
Original line number Diff line number Diff line
@@ -372,10 +372,9 @@ static int alloc_pebs_buffer(int cpu) 
static void release_pebs_buffer(int cpu)

{

	struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu);

	struct debug_store *ds = hwev->ds;

	void *cea;



	if (!ds || !x86_pmu.pebs)

	if (!x86_pmu.pebs)

		return;



	kfree(per_cpu(insn_buffer, cpu));
@@ -384,7 +383,6 @@ static void release_pebs_buffer(int cpu) 
	/* Clear the fixmap */

	cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.pebs_buffer;

	ds_clear_cea(cea, x86_pmu.pebs_buffer_size);

	ds->pebs_buffer_base = 0;

	dsfree_pages(hwev->ds_pebs_vaddr, x86_pmu.pebs_buffer_size);

	hwev->ds_pebs_vaddr = NULL;

}
@@ -419,16 +417,14 @@ static int alloc_bts_buffer(int cpu) 
static void release_bts_buffer(int cpu)

{

	struct cpu_hw_events *hwev = per_cpu_ptr(&cpu_hw_events, cpu);

	struct debug_store *ds = hwev->ds;

	void *cea;



	if (!ds || !x86_pmu.bts)

	if (!x86_pmu.bts)

		return;



	/* Clear the fixmap */

	cea = &get_cpu_entry_area(cpu)->cpu_debug_buffers.bts_buffer;

	ds_clear_cea(cea, BTS_BUFFER_SIZE);

	ds->bts_buffer_base = 0;

	dsfree_pages(hwev->ds_bts_vaddr, BTS_BUFFER_SIZE);

	hwev->ds_bts_vaddr = NULL;

}
@@ -454,16 +450,22 @@ void release_ds_buffers(void) 
	if (!x86_pmu.bts && !x86_pmu.pebs)

		return;



	get_online_cpus();

	for_each_online_cpu(cpu)

	for_each_possible_cpu(cpu)

		release_ds_buffer(cpu);



	for_each_possible_cpu(cpu) {

		/*

		 * Again, ignore errors from offline CPUs, they will no longer

		 * observe cpu_hw_events.ds and not program the DS_AREA when

		 * they come up.

		 */

		fini_debug_store_on_cpu(cpu);

	}



	for_each_possible_cpu(cpu) {

		release_pebs_buffer(cpu);

		release_bts_buffer(cpu);

		release_ds_buffer(cpu);

	}

	put_online_cpus();

}



void reserve_ds_buffers(void)
@@ -483,8 +485,6 @@ void reserve_ds_buffers(void) 
	if (!x86_pmu.pebs)

		pebs_err = 1;



	get_online_cpus();



	for_each_possible_cpu(cpu) {

		if (alloc_ds_buffer(cpu)) {

			bts_err = 1;
@@ -521,11 +521,14 @@ void reserve_ds_buffers(void) 
		if (x86_pmu.pebs && !pebs_err)

			x86_pmu.pebs_active = 1;



		for_each_online_cpu(cpu)

		for_each_possible_cpu(cpu) {

			/*

			 * Ignores wrmsr_on_cpu() errors for offline CPUs they

			 * will get this call through intel_pmu_cpu_starting().

			 */

			init_debug_store_on_cpu(cpu);

		}



	put_online_cpus();

	}

}



/*