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: Peter 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: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 8156e47da7ba4c5a31e9f9436b27a96cfb7da4c3..18c25ab2855744142d836f311e0b1a9279f2ed06 100644 (file)
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -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();
 }
 
 /*