6.10-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner tglx@linutronix.de
[ Upstream commit bb9bb45f746b0f9457de9c3fc4da143a6351bdc9 ]
Yue and Xingwei reported a jump label failure. It's caused by the lack of serialization in set_attr_rdpmc():
CPU0 CPU1
Assume: x86_pmu.attr_rdpmc == 0
if (val != x86_pmu.attr_rdpmc) { if (val == 0) ... else if (x86_pmu.attr_rdpmc == 0) static_branch_dec(&rdpmc_never_available_key);
if (val != x86_pmu.attr_rdpmc) { if (val == 0) ... else if (x86_pmu.attr_rdpmc == 0) FAIL, due to imbalance ---> static_branch_dec(&rdpmc_never_available_key);
The reported BUG() is a consequence of the above and of another bug in the jump label core code. The core code needs a separate fix, but that cannot prevent the imbalance problem caused by set_attr_rdpmc().
Prevent this by serializing set_attr_rdpmc() locally.
Fixes: a66734297f78 ("perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks") Closes: https://lore.kernel.org/r/CAEkJfYNzfW1vG=ZTMdz_Weoo=RXY1NDunbxnDaLyj8R4kEoE_... Reported-by: Yue Sun samsun1006219@gmail.com Reported-by: Xingwei Lee xrivendell7@gmail.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/20240610124406.359476013@linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/events/core.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 5b0dd07b1ef19..acd367c453341 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2547,6 +2547,7 @@ static ssize_t set_attr_rdpmc(struct device *cdev, struct device_attribute *attr, const char *buf, size_t count) { + static DEFINE_MUTEX(rdpmc_mutex); unsigned long val; ssize_t ret;
@@ -2560,6 +2561,8 @@ static ssize_t set_attr_rdpmc(struct device *cdev, if (x86_pmu.attr_rdpmc_broken) return -ENOTSUPP;
+ guard(mutex)(&rdpmc_mutex); + if (val != x86_pmu.attr_rdpmc) { /* * Changing into or out of never available or always available,