diff options
Diffstat (limited to 'features/rt/locking-rtmutex-Use-custom-scheduling-function-for-s.patch')
| -rw-r--r-- | features/rt/locking-rtmutex-Use-custom-scheduling-function-for-s.patch | 242 |
1 files changed, 242 insertions, 0 deletions
diff --git a/features/rt/locking-rtmutex-Use-custom-scheduling-function-for-s.patch b/features/rt/locking-rtmutex-Use-custom-scheduling-function-for-s.patch new file mode 100644 index 00000000..3ba23b2f --- /dev/null +++ b/features/rt/locking-rtmutex-Use-custom-scheduling-function-for-s.patch @@ -0,0 +1,242 @@ +From 7e9de9093f6ab9c69a00c038c12e21054214f301 Mon Sep 17 00:00:00 2001 +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Tue, 6 Oct 2020 13:07:17 +0200 +Subject: [PATCH 082/191] locking/rtmutex: Use custom scheduling function for + spin-schedule() + +PREEMPT_RT builds the rwsem, mutex, spinlock and rwlock typed locks on +top of a rtmutex lock. While blocked task->pi_blocked_on is set +(tsk_is_pi_blocked()) and task needs to schedule away while waiting. + +The schedule process must distinguish between blocking on a regular +sleeping lock (rwsem and mutex) and a RT-only sleeping lock (spinlock +and rwlock): +- rwsem and mutex must flush block requests (blk_schedule_flush_plug()) + even if blocked on a lock. This can not deadlock because this also + happens for non-RT. + There should be a warning if the scheduling point is within a RCU read + section. + +- spinlock and rwlock must not flush block requests. This will deadlock + if the callback attempts to acquire a lock which is already acquired. + Similarly to being preempted, there should be no warning if the + scheduling point is within a RCU read section. + +Add preempt_schedule_lock() which is invoked if scheduling is required +while blocking on a PREEMPT_RT-only sleeping lock. +Remove tsk_is_pi_blocked() from the scheduler path which is no longer +needed with the additional scheduler entry point. + +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + arch/arm64/include/asm/preempt.h | 3 +++ + arch/x86/include/asm/preempt.h | 3 +++ + include/asm-generic/preempt.h | 3 +++ + include/linux/sched/rt.h | 8 -------- + kernel/locking/rtmutex.c | 2 +- + kernel/locking/rwlock-rt.c | 2 +- + kernel/sched/core.c | 32 +++++++++++++++++++++----------- + 7 files changed, 32 insertions(+), 21 deletions(-) + +diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h +index 80e946b2abee..f06a23898540 100644 +--- a/arch/arm64/include/asm/preempt.h ++++ b/arch/arm64/include/asm/preempt.h +@@ -81,6 +81,9 @@ static inline bool should_resched(int preempt_offset) + + #ifdef CONFIG_PREEMPTION + void preempt_schedule(void); ++#ifdef CONFIG_PREEMPT_RT ++void preempt_schedule_lock(void); ++#endif + #define __preempt_schedule() preempt_schedule() + void preempt_schedule_notrace(void); + #define __preempt_schedule_notrace() preempt_schedule_notrace() +diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h +index f8cb8af4de5c..7e0358f99d22 100644 +--- a/arch/x86/include/asm/preempt.h ++++ b/arch/x86/include/asm/preempt.h +@@ -104,6 +104,9 @@ static __always_inline bool should_resched(int preempt_offset) + } + + #ifdef CONFIG_PREEMPTION ++#ifdef CONFIG_PREEMPT_RT ++ extern void preempt_schedule_lock(void); ++#endif + + extern asmlinkage void preempt_schedule(void); + extern asmlinkage void preempt_schedule_thunk(void); +diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h +index d683f5e6d791..71c1535db56a 100644 +--- a/include/asm-generic/preempt.h ++++ b/include/asm-generic/preempt.h +@@ -79,6 +79,9 @@ static __always_inline bool should_resched(int preempt_offset) + } + + #ifdef CONFIG_PREEMPTION ++#ifdef CONFIG_PREEMPT_RT ++extern void preempt_schedule_lock(void); ++#endif + extern asmlinkage void preempt_schedule(void); + #define __preempt_schedule() preempt_schedule() + extern asmlinkage void preempt_schedule_notrace(void); +diff --git a/include/linux/sched/rt.h b/include/linux/sched/rt.h +index e5af028c08b4..994c25640e15 100644 +--- a/include/linux/sched/rt.h ++++ b/include/linux/sched/rt.h +@@ -39,20 +39,12 @@ static inline struct task_struct *rt_mutex_get_top_task(struct task_struct *p) + } + extern void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task); + extern void rt_mutex_adjust_pi(struct task_struct *p); +-static inline bool tsk_is_pi_blocked(struct task_struct *tsk) +-{ +- return tsk->pi_blocked_on != NULL; +-} + #else + static inline struct task_struct *rt_mutex_get_top_task(struct task_struct *task) + { + return NULL; + } + # define rt_mutex_adjust_pi(p) do { } while (0) +-static inline bool tsk_is_pi_blocked(struct task_struct *tsk) +-{ +- return false; +-} + #endif + + extern void normalize_rt_tasks(void); +diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c +index 3fc947dd2e60..4cd9d6c4cd68 100644 +--- a/kernel/locking/rtmutex.c ++++ b/kernel/locking/rtmutex.c +@@ -1049,7 +1049,7 @@ void __sched rt_spin_lock_slowlock_locked(struct rt_mutex *lock, + raw_spin_unlock_irqrestore(&lock->wait_lock, flags); + + if (top_waiter != waiter || adaptive_wait(lock, lock_owner)) +- schedule(); ++ preempt_schedule_lock(); + + raw_spin_lock_irqsave(&lock->wait_lock, flags); + +diff --git a/kernel/locking/rwlock-rt.c b/kernel/locking/rwlock-rt.c +index 64c4f5728b11..948d10214ee2 100644 +--- a/kernel/locking/rwlock-rt.c ++++ b/kernel/locking/rwlock-rt.c +@@ -211,7 +211,7 @@ static void __write_rt_lock(struct rt_rw_lock *lock) + raw_spin_unlock_irqrestore(&m->wait_lock, flags); + + if (atomic_read(&lock->readers) != 0) +- schedule(); ++ preempt_schedule_lock(); + + raw_spin_lock_irqsave(&m->wait_lock, flags); + +diff --git a/kernel/sched/core.c b/kernel/sched/core.c +index 46e7db92b343..59fb8b18799f 100644 +--- a/kernel/sched/core.c ++++ b/kernel/sched/core.c +@@ -5004,7 +5004,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) + * + * WARNING: must be called with preemption disabled! + */ +-static void __sched notrace __schedule(bool preempt) ++static void __sched notrace __schedule(bool preempt, bool spinning_lock) + { + struct task_struct *prev, *next; + unsigned long *switch_count; +@@ -5057,7 +5057,7 @@ static void __sched notrace __schedule(bool preempt) + * - ptrace_{,un}freeze_traced() can change ->state underneath us. + */ + prev_state = prev->state; +- if (!preempt && prev_state) { ++ if ((!preempt || spinning_lock) && prev_state) { + if (signal_pending_state(prev_state, prev)) { + prev->state = TASK_RUNNING; + } else { +@@ -5141,7 +5141,7 @@ void __noreturn do_task_dead(void) + /* Tell freezer to ignore us: */ + current->flags |= PF_NOFREEZE; + +- __schedule(false); ++ __schedule(false, false); + BUG(); + + /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */ +@@ -5174,9 +5174,6 @@ static inline void sched_submit_work(struct task_struct *tsk) + preempt_enable_no_resched(); + } + +- if (tsk_is_pi_blocked(tsk)) +- return; +- + /* + * If we are going to sleep and we have plugged IO queued, + * make sure to submit it to avoid deadlocks. +@@ -5202,7 +5199,7 @@ asmlinkage __visible void __sched schedule(void) + sched_submit_work(tsk); + do { + preempt_disable(); +- __schedule(false); ++ __schedule(false, false); + sched_preempt_enable_no_resched(); + } while (need_resched()); + sched_update_worker(tsk); +@@ -5230,7 +5227,7 @@ void __sched schedule_idle(void) + */ + WARN_ON_ONCE(current->state); + do { +- __schedule(false); ++ __schedule(false, false); + } while (need_resched()); + } + +@@ -5283,7 +5280,7 @@ static void __sched notrace preempt_schedule_common(void) + */ + preempt_disable_notrace(); + preempt_latency_start(1); +- __schedule(true); ++ __schedule(true, false); + preempt_latency_stop(1); + preempt_enable_no_resched_notrace(); + +@@ -5313,6 +5310,19 @@ asmlinkage __visible void __sched notrace preempt_schedule(void) + NOKPROBE_SYMBOL(preempt_schedule); + EXPORT_SYMBOL(preempt_schedule); + ++#ifdef CONFIG_PREEMPT_RT ++void __sched notrace preempt_schedule_lock(void) ++{ ++ do { ++ preempt_disable(); ++ __schedule(true, true); ++ sched_preempt_enable_no_resched(); ++ } while (need_resched()); ++} ++NOKPROBE_SYMBOL(preempt_schedule_lock); ++EXPORT_SYMBOL(preempt_schedule_lock); ++#endif ++ + #ifdef CONFIG_PREEMPT_DYNAMIC + DEFINE_STATIC_CALL(preempt_schedule, __preempt_schedule_func); + EXPORT_STATIC_CALL_TRAMP(preempt_schedule); +@@ -5362,7 +5372,7 @@ asmlinkage __visible void __sched notrace preempt_schedule_notrace(void) + * an infinite recursion. + */ + prev_ctx = exception_enter(); +- __schedule(true); ++ __schedule(true, false); + exception_exit(prev_ctx); + + preempt_latency_stop(1); +@@ -5580,7 +5590,7 @@ asmlinkage __visible void __sched preempt_schedule_irq(void) + do { + preempt_disable(); + local_irq_enable(); +- __schedule(true); ++ __schedule(true, false); + local_irq_disable(); + sched_preempt_enable_no_resched(); + } while (need_resched()); +-- +2.19.1 + |