summaryrefslogtreecommitdiffstats
path: root/debian/patches-rt/0070-notifier-Make-atomic_notifiers-use-raw_spinlock.patch
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--debian/patches-rt/0070-notifier-Make-atomic_notifiers-use-raw_spinlock.patch132
1 files changed, 132 insertions, 0 deletions
diff --git a/debian/patches-rt/0070-notifier-Make-atomic_notifiers-use-raw_spinlock.patch b/debian/patches-rt/0070-notifier-Make-atomic_notifiers-use-raw_spinlock.patch
new file mode 100644
index 000000000..74ee5109b
--- /dev/null
+++ b/debian/patches-rt/0070-notifier-Make-atomic_notifiers-use-raw_spinlock.patch
@@ -0,0 +1,132 @@
+From f603fbc6eaf37d836e3498b47cef43965730bcda 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 070/323] notifier: Make atomic_notifiers use raw_spinlock
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
+
+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;
+ }
+--
+2.43.0
+