diff options
Diffstat (limited to 'features/rt/sched-Add-saved_state-for-tasks-blocked-on-sleeping-.patch')
| -rw-r--r-- | features/rt/sched-Add-saved_state-for-tasks-blocked-on-sleeping-.patch | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/features/rt/sched-Add-saved_state-for-tasks-blocked-on-sleeping-.patch b/features/rt/sched-Add-saved_state-for-tasks-blocked-on-sleeping-.patch new file mode 100644 index 00000000..8de24806 --- /dev/null +++ b/features/rt/sched-Add-saved_state-for-tasks-blocked-on-sleeping-.patch @@ -0,0 +1,115 @@ +From 34b399662682e7d121a12d7f11c06f809c60d085 Mon Sep 17 00:00:00 2001 +From: Thomas Gleixner <tglx@linutronix.de> +Date: Sat, 25 Jun 2011 09:21:04 +0200 +Subject: [PATCH 074/191] sched: Add saved_state for tasks blocked on sleeping + locks + +Spinlocks are state preserving in !RT. RT changes the state when a +task gets blocked on a lock. So we need to remember the state before +the lock contention. If a regular wakeup (not a RTmutex related +wakeup) happens, the saved_state is updated to running. When the lock +sleep is done, the saved state is restored. + +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +--- + include/linux/sched.h | 3 +++ + kernel/sched/core.c | 34 ++++++++++++++++++++++++++++++++-- + kernel/sched/sched.h | 1 + + 3 files changed, 36 insertions(+), 2 deletions(-) + +diff --git a/include/linux/sched.h b/include/linux/sched.h +index c8998312d7bc..3f05b8c29132 100644 +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -655,6 +655,8 @@ struct task_struct { + #endif + /* -1 unrunnable, 0 runnable, >0 stopped: */ + volatile long state; ++ /* saved state for "spinlock sleepers" */ ++ volatile long saved_state; + + /* + * This begins the randomizable portion of task_struct. Only +@@ -1780,6 +1782,7 @@ extern struct task_struct *find_get_task_by_vpid(pid_t nr); + + extern int wake_up_state(struct task_struct *tsk, unsigned int state); + extern int wake_up_process(struct task_struct *tsk); ++extern int wake_up_lock_sleeper(struct task_struct *tsk); + extern void wake_up_new_task(struct task_struct *tsk); + + #ifdef CONFIG_SMP +diff --git a/kernel/sched/core.c b/kernel/sched/core.c +index 98191218d891..4efe6fd72719 100644 +--- a/kernel/sched/core.c ++++ b/kernel/sched/core.c +@@ -3314,7 +3314,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) + int cpu, success = 0; + + preempt_disable(); +- if (p == current) { ++ if (!IS_ENABLED(CONFIG_PREEMPT_RT) && p == current) { + /* + * We're waking current, this means 'p->on_rq' and 'task_cpu(p) + * == smp_processor_id()'. Together this means we can special +@@ -3344,8 +3344,26 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) + */ + raw_spin_lock_irqsave(&p->pi_lock, flags); + smp_mb__after_spinlock(); +- if (!(p->state & state)) ++ if (!(p->state & state)) { ++ /* ++ * The task might be running due to a spinlock sleeper ++ * wakeup. Check the saved state and set it to running ++ * if the wakeup condition is true. ++ */ ++ if (!(wake_flags & WF_LOCK_SLEEPER)) { ++ if (p->saved_state & state) { ++ p->saved_state = TASK_RUNNING; ++ success = 1; ++ } ++ } + goto unlock; ++ } ++ /* ++ * If this is a regular wakeup, then we can unconditionally ++ * clear the saved state of a "lock sleeper". ++ */ ++ if (!(wake_flags & WF_LOCK_SLEEPER)) ++ p->saved_state = TASK_RUNNING; + + trace_sched_waking(p); + +@@ -3534,6 +3552,18 @@ int wake_up_process(struct task_struct *p) + } + EXPORT_SYMBOL(wake_up_process); + ++/** ++ * wake_up_lock_sleeper - Wake up a specific process blocked on a "sleeping lock" ++ * @p: The process to be woken up. ++ * ++ * Same as wake_up_process() above, but wake_flags=WF_LOCK_SLEEPER to indicate ++ * the nature of the wakeup. ++ */ ++int wake_up_lock_sleeper(struct task_struct *p) ++{ ++ return try_to_wake_up(p, TASK_UNINTERRUPTIBLE, WF_LOCK_SLEEPER); ++} ++ + int wake_up_state(struct task_struct *p, unsigned int state) + { + return try_to_wake_up(p, state, 0); +diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h +index 10a1522b1e30..b65a4e244a77 100644 +--- a/kernel/sched/sched.h ++++ b/kernel/sched/sched.h +@@ -1751,6 +1751,7 @@ static inline int task_on_rq_migrating(struct task_struct *p) + #define WF_SYNC 0x10 /* Waker goes to sleep after wakeup */ + #define WF_MIGRATED 0x20 /* Internal use, task got migrated */ + #define WF_ON_CPU 0x40 /* Wakee is on_cpu */ ++#define WF_LOCK_SLEEPER 0x80 /* Wakeup spinlock "sleeper" */ + + #ifdef CONFIG_SMP + static_assert(WF_EXEC == SD_BALANCE_EXEC); +-- +2.19.1 + |