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Message-ID: <172984332942.1442.8807119394229092755.tip-bot2@tip-bot2>
Date: Fri, 25 Oct 2024 08:02:09 -0000
From: "tip-bot2 for Kan Liang" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Paul E. McKenney" <paulmck@...nel.org>,
kernel test robot <oliver.sang@...el.com>,
Peter Zijlstra <peterz@...radead.org>, Kan Liang <kan.liang@...ux.intel.com>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: perf/urgent] perf: Fix missing RCU reader protection in
perf_event_clear_cpumask()
The following commit has been merged into the perf/urgent branch of tip:
Commit-ID: e3dfd64c1f344ebec9397719244c27b360255855
Gitweb: https://git.kernel.org/tip/e3dfd64c1f344ebec9397719244c27b360255855
Author: Kan Liang <kan.liang@...ux.intel.com>
AuthorDate: Fri, 13 Sep 2024 09:23:40 -07:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 23 Oct 2024 20:52:25 +02:00
perf: Fix missing RCU reader protection in perf_event_clear_cpumask()
Running rcutorture scenario TREE05, the below warning is triggered.
[ 32.604594] WARNING: suspicious RCU usage
[ 32.605928] 6.11.0-rc5-00040-g4ba4f1afb6a9 #55238 Not tainted
[ 32.607812] -----------------------------
[ 32.609140] kernel/events/core.c:13946 RCU-list traversed in non-reader section!!
[ 32.611595] other info that might help us debug this:
[ 32.614247] rcu_scheduler_active = 2, debug_locks = 1
[ 32.616392] 3 locks held by cpuhp/4/35:
[ 32.617687] #0: ffffffffb666a650 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x4e/0x200
[ 32.620563] #1: ffffffffb666cd20 (cpuhp_state-down){+.+.}-{0:0}, at: cpuhp_thread_fun+0x4e/0x200
[ 32.623412] #2: ffffffffb677c288 (pmus_lock){+.+.}-{3:3}, at: perf_event_exit_cpu_context+0x32/0x2f0
In perf_event_clear_cpumask(), uses list_for_each_entry_rcu() without an
obvious RCU read-side critical section.
Either pmus_srcu or pmus_lock is good enough to protect the pmus list.
In the current context, pmus_lock is already held. The
list_for_each_entry_rcu() is not required.
Fixes: 4ba4f1afb6a9 ("perf: Generic hotplug support for a PMU with a scope")
Closes: https://lore.kernel.org/lkml/2b66dff8-b827-494b-b151-1ad8d56f13e6@paulmck-laptop/
Closes: https://lore.kernel.org/oe-lkp/202409131559.545634cc-oliver.sang@intel.com
Reported-by: "Paul E. McKenney" <paulmck@...nel.org>
Reported-by: kernel test robot <oliver.sang@...el.com>
Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: "Paul E. McKenney" <paulmck@...nel.org>
Link: https://lore.kernel.org/r/20240913162340.2142976-1-kan.liang@linux.intel.com
---
kernel/events/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index cdd0976..df27d08 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -13959,7 +13959,7 @@ static void perf_event_clear_cpumask(unsigned int cpu)
}
/* migrate */
- list_for_each_entry_rcu(pmu, &pmus, entry, lockdep_is_held(&pmus_srcu)) {
+ list_for_each_entry(pmu, &pmus, entry) {
if (pmu->scope == PERF_PMU_SCOPE_NONE ||
WARN_ON_ONCE(pmu->scope >= PERF_PMU_MAX_SCOPE))
continue;
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