On Thu, 18 Jun 2015, Thomas Gleixner wrote:
On Thu, 18 Jun 2015, Kanaka Juvva wrote:
Added lock in event reader function. The cqm_pick_event_reader() function
accesses cqm_cpumask and it is critical section between this and
cqm_stable().
This situation is true when a CPU is hotplugged. Mutex is used to protect
the critical section.
Signed-off-by: Kanaka Juvva <[email protected]>
---
arch/x86/kernel/cpu/perf_event_intel_cqm.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_cqm.c
b/arch/x86/kernel/cpu/perf_event_intel_cqm.c
index 1880761..e17e37f 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_cqm.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_cqm.c
@@ -1239,12 +1239,15 @@ static inline void cqm_pick_event_reader(int cpu)
int phys_id = topology_physical_package_id(cpu);
int i;
+ mutex_lock(&cache_mutex);
I already explained it to Vikas. You CANNOT take a mutex in that code
path as it runs with interrupts disabled on a CPU which cannot
schedule.
This patch also needs to be merged with the new package mask changes that
was added.
Will merge and send the fix.
Thanks,
Vikas
Sigh.
tglx
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