diff options
author | Valentin Schneider <valentin.schneider@arm.com> | 2020-11-22 20:19:04 +0000 |
---|---|---|
committer | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2020-11-30 18:21:09 +0100 |
commit | 23d5e0d7db656ae130461094ea52e62b6e65d65e (patch) | |
tree | 2a9e552b393f0f901b93ff7553e41adafdba37f1 | |
parent | fd4539f875ef12c44e24beccefe31061a46b5102 (diff) | |
download | linux-rt-23d5e0d7db656ae130461094ea52e62b6e65d65e.tar.gz |
notifier: Make atomic_notifiers use raw_spinlock
Booting a recent PREEMPT_RT kernel (v5.10-rc3-rt7-rebase) on my arm64 Juno
leads to the idle task blocking on an RT sleeping spinlock down some
notifier path:
[ 1.809101] BUG: scheduling while atomic: swapper/5/0/0x00000002
[ 1.809116] Modules linked in:
[ 1.809123] Preemption disabled at:
[ 1.809125] secondary_start_kernel (arch/arm64/kernel/smp.c:227)
[ 1.809146] CPU: 5 PID: 0 Comm: swapper/5 Tainted: G W 5.10.0-rc3-rt7 #168
[ 1.809153] Hardware name: ARM Juno development board (r0) (DT)
[ 1.809158] Call trace:
[ 1.809160] dump_backtrace (arch/arm64/kernel/stacktrace.c:100 (discriminator 1))
[ 1.809170] show_stack (arch/arm64/kernel/stacktrace.c:198)
[ 1.809178] dump_stack (lib/dump_stack.c:122)
[ 1.809188] __schedule_bug (kernel/sched/core.c:4886)
[ 1.809197] __schedule (./arch/arm64/include/asm/preempt.h:18 kernel/sched/core.c:4913 kernel/sched/core.c:5040)
[ 1.809204] preempt_schedule_lock (kernel/sched/core.c:5365 (discriminator 1))
[ 1.809210] rt_spin_lock_slowlock_locked (kernel/locking/rtmutex.c:1072)
[ 1.809217] rt_spin_lock_slowlock (kernel/locking/rtmutex.c:1110)
[ 1.809224] rt_spin_lock (./include/linux/rcupdate.h:647 kernel/locking/rtmutex.c:1139)
[ 1.809231] atomic_notifier_call_chain_robust (kernel/notifier.c:71 kernel/notifier.c:118 kernel/notifier.c:186)
[ 1.809240] cpu_pm_enter (kernel/cpu_pm.c:39 kernel/cpu_pm.c:93)
[ 1.809249] psci_enter_idle_state (drivers/cpuidle/cpuidle-psci.c:52 drivers/cpuidle/cpuidle-psci.c:129)
[ 1.809258] cpuidle_enter_state (drivers/cpuidle/cpuidle.c:238)
[ 1.809267] cpuidle_enter (drivers/cpuidle/cpuidle.c:353)
[ 1.809275] do_idle (kernel/sched/idle.c:132 kernel/sched/idle.c:213 kernel/sched/idle.c:273)
[ 1.809282] cpu_startup_entry (kernel/sched/idle.c:368 (discriminator 1))
[ 1.809288] secondary_start_kernel (arch/arm64/kernel/smp.c:273)
Two points worth noting:
1) That this is conceptually the same issue as pointed out in:
313c8c16ee62 ("PM / CPU: replace raw_notifier with atomic_notifier")
2) Only the _robust() variant of atomic_notifier callchains suffer from
this
AFAICT only the cpu_pm_notifier_chain really needs to be changed, but
singling it out would mean introducing a new (truly) non-blocking API. At
the same time, callers that are fine with any blocking within the call
chain should use blocking notifiers, so patching up all atomic_notifier's
doesn't seem *too* crazy to me.
Fixes: 70d932985757 ("notifier: Fix broken error handling pattern")
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Link: https://lkml.kernel.org/r/20201122201904.30940-1-valentin.schneider@arm.com
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
-rw-r--r-- | include/linux/notifier.h | 6 | ||||
-rw-r--r-- | kernel/notifier.c | 12 |
2 files changed, 9 insertions, 9 deletions
diff --git a/include/linux/notifier.h b/include/linux/notifier.h index 2fb373a5c1ed..723bc2df6388 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -58,7 +58,7 @@ struct notifier_block { }; struct atomic_notifier_head { - spinlock_t lock; + raw_spinlock_t lock; struct notifier_block __rcu *head; }; @@ -78,7 +78,7 @@ struct srcu_notifier_head { }; #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ - spin_lock_init(&(name)->lock); \ + raw_spin_lock_init(&(name)->lock); \ (name)->head = NULL; \ } while (0) #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \ @@ -95,7 +95,7 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); cleanup_srcu_struct(&(name)->srcu); #define ATOMIC_NOTIFIER_INIT(name) { \ - .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ + .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \ .head = NULL } #define BLOCKING_NOTIFIER_INIT(name) { \ .rwsem = __RWSEM_INITIALIZER((name).rwsem), \ diff --git a/kernel/notifier.c b/kernel/notifier.c index 1b019cbca594..c20782f07643 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -142,9 +142,9 @@ int atomic_notifier_chain_register(struct atomic_notifier_head *nh, unsigned long flags; int ret; - spin_lock_irqsave(&nh->lock, flags); + raw_spin_lock_irqsave(&nh->lock, flags); ret = notifier_chain_register(&nh->head, n); - spin_unlock_irqrestore(&nh->lock, flags); + raw_spin_unlock_irqrestore(&nh->lock, flags); return ret; } EXPORT_SYMBOL_GPL(atomic_notifier_chain_register); @@ -164,9 +164,9 @@ int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, unsigned long flags; int ret; - spin_lock_irqsave(&nh->lock, flags); + raw_spin_lock_irqsave(&nh->lock, flags); ret = notifier_chain_unregister(&nh->head, n); - spin_unlock_irqrestore(&nh->lock, flags); + raw_spin_unlock_irqrestore(&nh->lock, flags); synchronize_rcu(); return ret; } @@ -182,9 +182,9 @@ int atomic_notifier_call_chain_robust(struct atomic_notifier_head *nh, * Musn't use RCU; because then the notifier list can * change between the up and down traversal. */ - spin_lock_irqsave(&nh->lock, flags); + raw_spin_lock_irqsave(&nh->lock, flags); ret = notifier_call_chain_robust(&nh->head, val_up, val_down, v); - spin_unlock_irqrestore(&nh->lock, flags); + raw_spin_unlock_irqrestore(&nh->lock, flags); return ret; } |