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authorLike Xu <like.xu@linux.intel.com>2021-04-30 13:22:47 +0800
committerPeter Zijlstra <peterz@infradead.org>2021-05-18 12:53:47 +0200
commit488e13a489e9707a7e81e1991fdd1f20c0f04689 (patch)
tree879e930522ad4021a4118c8ff0e9d5ae0d869917
parent3317c26a4b413b41364f2c4b83c778c6aba1576d (diff)
perf/x86/lbr: Remove cpuc->lbr_xsave allocation from atomic context
If the kernel is compiled with the CONFIG_LOCKDEP option, the conditional might_sleep_if() deep in kmem_cache_alloc() will generate the following trace, and potentially cause a deadlock when another LBR event is added: [] BUG: sleeping function called from invalid context at include/linux/sched/mm.h:196 [] Call Trace: [] kmem_cache_alloc+0x36/0x250 [] intel_pmu_lbr_add+0x152/0x170 [] x86_pmu_add+0x83/0xd0 Make it symmetric with the release_lbr_buffers() call and mirror the existing DS buffers. Fixes: c085fb8774 ("perf/x86/intel/lbr: Support XSAVES for arch LBR read") Signed-off-by: Like Xu <like.xu@linux.intel.com> [peterz: simplified] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Kan Liang <kan.liang@linux.intel.com> Link: https://lkml.kernel.org/r/20210430052247.3079672-2-like.xu@linux.intel.com
-rw-r--r--arch/x86/events/core.c6
-rw-r--r--arch/x86/events/intel/lbr.c26
-rw-r--r--arch/x86/events/perf_event.h6
3 files changed, 30 insertions, 8 deletions
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 8e509325c2c3..8f71dd72ef95 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -396,10 +396,12 @@ int x86_reserve_hardware(void)
if (!atomic_inc_not_zero(&pmc_refcount)) {
mutex_lock(&pmc_reserve_mutex);
if (atomic_read(&pmc_refcount) == 0) {
- if (!reserve_pmc_hardware())
+ if (!reserve_pmc_hardware()) {
err = -EBUSY;
- else
+ } else {
reserve_ds_buffers();
+ reserve_lbr_buffers();
+ }
}
if (!err)
atomic_inc(&pmc_refcount);
diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 76dbab6ac9fb..4409d2cccfda 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -658,7 +658,6 @@ static inline bool branch_user_callstack(unsigned br_sel)
void intel_pmu_lbr_add(struct perf_event *event)
{
- struct kmem_cache *kmem_cache = event->pmu->task_ctx_cache;
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
if (!x86_pmu.lbr_nr)
@@ -696,11 +695,6 @@ void intel_pmu_lbr_add(struct perf_event *event)
perf_sched_cb_inc(event->ctx->pmu);
if (!cpuc->lbr_users++ && !event->total_time_running)
intel_pmu_lbr_reset();
-
- if (static_cpu_has(X86_FEATURE_ARCH_LBR) &&
- kmem_cache && !cpuc->lbr_xsave &&
- (cpuc->lbr_users != cpuc->lbr_pebs_users))
- cpuc->lbr_xsave = kmem_cache_alloc(kmem_cache, GFP_KERNEL);
}
void release_lbr_buffers(void)
@@ -722,6 +716,26 @@ void release_lbr_buffers(void)
}
}
+void reserve_lbr_buffers(void)
+{
+ struct kmem_cache *kmem_cache;
+ struct cpu_hw_events *cpuc;
+ int cpu;
+
+ if (!static_cpu_has(X86_FEATURE_ARCH_LBR))
+ return;
+
+ for_each_possible_cpu(cpu) {
+ cpuc = per_cpu_ptr(&cpu_hw_events, cpu);
+ kmem_cache = x86_get_pmu(cpu)->task_ctx_cache;
+ if (!kmem_cache || cpuc->lbr_xsave)
+ continue;
+
+ cpuc->lbr_xsave = kmem_cache_alloc_node(kmem_cache, GFP_KERNEL,
+ cpu_to_node(cpu));
+ }
+}
+
void intel_pmu_lbr_del(struct perf_event *event)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 27fa85e7d4fd..ad87cb36f7c8 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1244,6 +1244,8 @@ void reserve_ds_buffers(void);
void release_lbr_buffers(void);
+void reserve_lbr_buffers(void);
+
extern struct event_constraint bts_constraint;
extern struct event_constraint vlbr_constraint;
@@ -1393,6 +1395,10 @@ static inline void release_lbr_buffers(void)
{
}
+static inline void reserve_lbr_buffers(void)
+{
+}
+
static inline int intel_pmu_init(void)
{
return 0;