From: Thomas Gleixner tglx@linutronix.de

mainline inclusion from mainline-v6.11-rc1 commit bb9bb45f746b0f9457de9c3fc4da143a6351bdc9 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IAMTVO

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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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 Conflicts: arch/x86/events/core.c [Using mutex_lock/mutex_unlock instead of guard] Signed-off-by: Luo Gengkun luogengkun2@huawei.com --- arch/x86/events/core.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index abdc814162d5..283aa4602eb1 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2529,6 +2529,7 @@ 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;

@@ -2542,6 +2543,8 @@ static ssize_t set_attr_rdpmc(struct device *cdev, if (x86_pmu.attr_rdpmc_broken) return -ENOTSUPP;

+ mutex_lock(&rdpmc_mutex); + if (val != x86_pmu.attr_rdpmc) { /* * Changing into or out of never available or always available, @@ -2562,6 +2565,8 @@ static ssize_t set_attr_rdpmc(struct device *cdev, x86_pmu.attr_rdpmc = val; }

+ mutex_unlock(&rdpmc_mutex); + return count; }