The patch titled
Subject: tracing/mm: don't trace mm_page_free on offline cpus
has been removed from the -mm tree. Its filename was
tracing-mm-dont-trace-mm_page_free-on-offline-cpus.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: "Shreyas B. Prabhu" <shreyas@xxxxxxxxxxxxxxxxxx>
Subject: tracing/mm: don't trace mm_page_free on offline cpus
Since tracepoints use RCU for protection, they must not be called on
offline cpus. trace_mm_page_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:170 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:
[c000001fed2f7790] [c0000000009dee8c] .dump_stack+0x98/0xd4 (unreliable)
[c000001fed2f7810] [c000000000128d88] .lockdep_rcu_suspicious+0x108/0x170
[c000001fed2f78a0] [c000000000203bc4] .free_pages_prepare+0x494/0x680
[c000001fed2f7980] [c000000000207fd0] .free_hot_cold_page+0x50/0x280
[c000001fed2f7a30] [c00000000004d000] .destroy_context+0x90/0xd0
[c000001fed2f7ab0] [c0000000000bd1d8] .__mmdrop+0x58/0x160
[c000001fed2f7b40] [c0000000001068e0] .idle_task_exit+0xf0/0x100
[c000001fed2f7bc0] [c000000000066948] .pnv_smp_cpu_kill_self+0x58/0x2c0
[c000001fed2f7ca0] [c00000000003ce34] .cpu_die+0x34/0x50
[c000001fed2f7d10] [c0000000000176d0] .arch_cpu_idle_dead+0x20/0x40
[c000001fed2f7d80] [c00000000011f9a8] .cpu_startup_entry+0x708/0x7a0
[c000001fed2f7ec0] [c00000000003cb6c] .start_secondary+0x36c/0x3a0
[c000001fed2f7f90] [c000000000008b6c] start_secondary_prolog+0x10/0x14
Fix this by converting mm_page_free trace point into TRACE_EVENT_CONDITION
where condition is cpu_online(smp_processor_id())
Signed-off-by: Shreyas B. Prabhu <shreyas@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/trace/events/kmem.h | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff -puN include/trace/events/kmem.h~tracing-mm-dont-trace-mm_page_free-on-offline-cpus include/trace/events/kmem.h
--- a/include/trace/events/kmem.h~tracing-mm-dont-trace-mm_page_free-on-offline-cpus
+++ a/include/trace/events/kmem.h
@@ -158,12 +158,24 @@ DEFINE_EVENT_CONDITION(kmem_free, kmem_c
TP_CONDITION(cpu_online(raw_smp_processor_id()))
);
-TRACE_EVENT(mm_page_free,
+TRACE_EVENT_CONDITION(mm_page_free,
TP_PROTO(struct page *page, unsigned int order),
TP_ARGS(page, order),
+
+ /*
+ * 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())),
+
TP_STRUCT__entry(
__field( unsigned long, pfn )
__field( unsigned int, order )
_
Patches currently in -mm which might be from shreyas@xxxxxxxxxxxxxxxxxx are
linux-next.patch
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