112 lines
3.9 KiB
Diff
112 lines
3.9 KiB
Diff
From 3dc003deb62cfddd8cfe666440d10e8abaa9e136 Mon Sep 17 00:00:00 2001
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Message-Id: <3dc003deb62cfddd8cfe666440d10e8abaa9e136.1601675152.git.zanussi@kernel.org>
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In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Sat, 25 Jun 2011 09:21:04 +0200
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Subject: [PATCH 109/333] sched: Add saved_state for tasks blocked on sleeping
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locks
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz
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Spinlocks are state preserving in !RT. RT changes the state when a
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task gets blocked on a lock. So we need to remember the state before
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the lock contention. If a regular wakeup (not a RTmutex related
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wakeup) happens, the saved_state is updated to running. When the lock
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sleep is done, the saved state is restored.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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include/linux/sched.h | 3 +++
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kernel/sched/core.c | 33 ++++++++++++++++++++++++++++++++-
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kernel/sched/sched.h | 1 +
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3 files changed, 36 insertions(+), 1 deletion(-)
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diff --git a/include/linux/sched.h b/include/linux/sched.h
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index 9a0e01e48602..42846a65df9a 100644
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--- a/include/linux/sched.h
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+++ b/include/linux/sched.h
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@@ -600,6 +600,8 @@ struct task_struct {
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#endif
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/* -1 unrunnable, 0 runnable, >0 stopped: */
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volatile long state;
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+ /* saved state for "spinlock sleepers" */
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+ volatile long saved_state;
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/*
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* This begins the randomizable portion of task_struct. Only
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@@ -1621,6 +1623,7 @@ extern struct task_struct *find_get_task_by_vpid(pid_t nr);
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extern int wake_up_state(struct task_struct *tsk, unsigned int state);
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extern int wake_up_process(struct task_struct *tsk);
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+extern int wake_up_lock_sleeper(struct task_struct *tsk);
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extern void wake_up_new_task(struct task_struct *tsk);
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#ifdef CONFIG_SMP
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diff --git a/kernel/sched/core.c b/kernel/sched/core.c
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index 3600139cb690..53d9f8927619 100644
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--- a/kernel/sched/core.c
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+++ b/kernel/sched/core.c
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@@ -1999,8 +1999,27 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
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*/
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raw_spin_lock_irqsave(&p->pi_lock, flags);
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smp_mb__after_spinlock();
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- if (!(p->state & state))
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+ if (!(p->state & state)) {
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+ /*
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+ * The task might be running due to a spinlock sleeper
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+ * wakeup. Check the saved state and set it to running
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+ * if the wakeup condition is true.
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+ */
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+ if (!(wake_flags & WF_LOCK_SLEEPER)) {
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+ if (p->saved_state & state) {
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+ p->saved_state = TASK_RUNNING;
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+ success = 1;
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+ }
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+ }
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goto out;
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+ }
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+
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+ /*
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+ * If this is a regular wakeup, then we can unconditionally
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+ * clear the saved state of a "lock sleeper".
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+ */
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+ if (!(wake_flags & WF_LOCK_SLEEPER))
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+ p->saved_state = TASK_RUNNING;
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trace_sched_waking(p);
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@@ -2164,6 +2183,18 @@ int wake_up_process(struct task_struct *p)
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}
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EXPORT_SYMBOL(wake_up_process);
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+/**
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+ * wake_up_lock_sleeper - Wake up a specific process blocked on a "sleeping lock"
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+ * @p: The process to be woken up.
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+ *
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+ * Same as wake_up_process() above, but wake_flags=WF_LOCK_SLEEPER to indicate
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+ * the nature of the wakeup.
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+ */
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+int wake_up_lock_sleeper(struct task_struct *p)
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+{
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+ return try_to_wake_up(p, TASK_UNINTERRUPTIBLE, WF_LOCK_SLEEPER);
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+}
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+
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int wake_up_state(struct task_struct *p, unsigned int state)
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{
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return try_to_wake_up(p, state, 0);
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diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
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index 5f0eb4565957..96823c632599 100644
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--- a/kernel/sched/sched.h
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+++ b/kernel/sched/sched.h
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@@ -1445,6 +1445,7 @@ static inline int task_on_rq_migrating(struct task_struct *p)
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#define WF_SYNC 0x01 /* Waker goes to sleep after wakeup */
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#define WF_FORK 0x02 /* Child wakeup after fork */
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#define WF_MIGRATED 0x4 /* Internal use, task got migrated */
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+#define WF_LOCK_SLEEPER 0x08 /* wakeup spinlock "sleeper" */
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/*
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* To aid in avoiding the subversion of "niceness" due to uneven distribution
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--
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2.17.1
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