From: "Paul E. McKenney" <paulmck@kernel.org>
To: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Cc: kan.liang@linux.intel.com, peterz@infradead.org,
mingo@redhat.com, acme@kernel.org, namhyung@kernel.org,
mark.rutland@arm.com, alexander.shishkin@linux.intel.com,
jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com
Subject: [BUG BISECTED] Missing RCU reader in perf_event_setup_cpumask()
Date: Fri, 13 Sep 2024 01:00:44 -0700 [thread overview]
Message-ID: <2b66dff8-b827-494b-b151-1ad8d56f13e6@paulmck-laptop> (raw)
Hello!
On next-20240912 running rcutorture scenario TREE05, I see this
deterministically:
[ 32.603233] =============================
[ 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]
[ 32.611595] other info that might help us debug this:
[ 32.611595]
[ 32.614247]
[ 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
[ 32.626399]
[ 32.626399] stack backtrace:
[ 32.627848] CPU: 4 UID: 0 PID: 35 Comm: cpuhp/4 Not tainted 6.11.0-rc5-00040-g4ba4f1afb6a9 #55238
[ 32.628832] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[ 32.628832] Call Trace:
[ 32.628832] <TASK>
[ 32.628832] dump_stack_lvl+0x83/0xa0
[ 32.628832] lockdep_rcu_suspicious+0x143/0x1a0
[ 32.628832] perf_event_exit_cpu_context+0x2e5/0x2f0
[ 32.628832] ? __pfx_perf_event_exit_cpu+0x10/0x10
[ 32.628832] perf_event_exit_cpu+0x9/0x10
[ 32.628832] cpuhp_invoke_callback+0x130/0x2a0
[ 32.628832] ? lock_release+0xc7/0x290
[ 32.628832] ? cpuhp_thread_fun+0x4e/0x200
[ 32.628832] cpuhp_thread_fun+0x183/0x200
[ 32.628832] smpboot_thread_fn+0xd8/0x1d0
[ 32.628832] ? __pfx_smpboot_thread_fn+0x10/0x10
[ 32.628832] kthread+0xd4/0x100
[ 32.628832] ? __pfx_kthread+0x10/0x10
[ 32.628832] ret_from_fork+0x2f/0x50
[ 32.628832] ? __pfx_kthread+0x10/0x10
[ 32.628832] ret_from_fork_asm+0x1a/0x30
[ 32.628832] </TASK>
I bisected this to:
4ba4f1afb6a9 ("perf: Generic hotplug support for a PMU with a scope")
This adds a perf_event_setup_cpumask() function that uses
list_for_each_entry_rcu() without an obvious RCU read-side critical
section, so the fix might be as simple as adding rcu_read_lock() and
rcu_read_unlock(). In the proper places, of course. ;-)
Thanx, Paul
next reply other threads:[~2024-09-13 8:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-13 8:00 Paul E. McKenney [this message]
2024-09-13 10:47 ` [BUG BISECTED] Missing RCU reader in perf_event_setup_cpumask() Peter Zijlstra
2024-09-13 12:09 ` Paul E. McKenney
2024-09-13 15:51 ` Liang, Kan
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