diff options
Diffstat (limited to 'features/rt/notifier-Make-atomic_notifiers-use-raw_spinlock.patch')
| -rw-r--r-- | features/rt/notifier-Make-atomic_notifiers-use-raw_spinlock.patch | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/features/rt/notifier-Make-atomic_notifiers-use-raw_spinlock.patch b/features/rt/notifier-Make-atomic_notifiers-use-raw_spinlock.patch new file mode 100644 index 00000000..9defbe15 --- /dev/null +++ b/features/rt/notifier-Make-atomic_notifiers-use-raw_spinlock.patch @@ -0,0 +1,131 @@ +From 074172587a9dfb0bae37a5663abb7e439376abfc Mon Sep 17 00:00:00 2001 +From: Valentin Schneider <valentin.schneider@arm.com> +Date: Sun, 22 Nov 2020 20:19:04 +0000 +Subject: [PATCH 005/191] 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> +--- + include/linux/notifier.h | 6 +++--- + 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; + } +-- +2.19.1 + |