From 488e13a489e9707a7e81e1991fdd1f20c0f04689 Mon Sep 17 00:00:00 2001 From: Like Xu Date: Fri, 30 Apr 2021 13:22:47 +0800 Subject: 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 [peterz: simplified] Signed-off-by: Peter Zijlstra (Intel) Tested-by: Kan Liang Link: https://lkml.kernel.org/r/20210430052247.3079672-2-like.xu@linux.intel.com --- arch/x86/events/intel/lbr.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) (limited to 'arch/x86/events/intel/lbr.c') 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); -- cgit