diff options
authorShreyas B. Prabhu <shreyas@linux.vnet.ibm.com>2015-05-28 15:44:16 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-05-28 18:25:18 -0700
commite5feb1ebaadfb1f5f70a3591e762d780232a4f5d (patch)
parentde182468d1bb726198abaab315820542425270b7 (diff)
tracing/mm: don't trace kmem_cache_free on offline cpus
Since tracepoints use RCU for protection, they must not be called on offline cpus. trace_kmem_cache_free can be called on an offline cpu in this scenario caught by LOCKDEP: =============================== [ INFO: suspicious RCU usage. ] 4.1.0-rc1+ #9 Not tainted ------------------------------- include/trace/events/kmem.h:148 suspicious rcu_dereference_check() usage! other info that might help us debug this: RCU used illegally from offline CPU! rcu_scheduler_active = 1, debug_locks = 1 no locks held by swapper/1/0. stack backtrace: CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.1.0-rc1+ #9 Call Trace: .dump_stack+0x98/0xd4 (unreliable) .lockdep_rcu_suspicious+0x108/0x170 .kmem_cache_free+0x344/0x4b0 .__mmdrop+0x4c/0x160 .idle_task_exit+0xf0/0x100 .pnv_smp_cpu_kill_self+0x58/0x2c0 .cpu_die+0x34/0x50 .arch_cpu_idle_dead+0x20/0x40 .cpu_startup_entry+0x708/0x7a0 .start_secondary+0x36c/0x3a0 start_secondary_prolog+0x10/0x14 Fix this by converting kmem_cache_free trace point into TRACE_EVENT_CONDITION where condition is cpu_online(smp_processor_id()) Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com> Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 13 insertions, 2 deletions
diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 81ea59812117..78efa0a197a9 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -140,11 +140,22 @@ DEFINE_EVENT(kmem_free, kfree,
TP_ARGS(call_site, ptr)
-DEFINE_EVENT(kmem_free, kmem_cache_free,
+DEFINE_EVENT_CONDITION(kmem_free, kmem_cache_free,
TP_PROTO(unsigned long call_site, const void *ptr),
- TP_ARGS(call_site, ptr)
+ TP_ARGS(call_site, ptr),
+ /*
+ * This trace can be potentially called from an offlined cpu.
+ * Since trace points use RCU and RCU should not be used from
+ * offline cpus, filter such calls out.
+ * While this trace can be called from a preemptable section,
+ * it has no impact on the condition since tasks can migrate
+ * only from online cpus to other online cpus. Thus its safe
+ * to use raw_smp_processor_id.
+ */
+ TP_CONDITION(cpu_online(raw_smp_processor_id()))