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locking/rtmutex: Prepare RT rt_mutex_wake_q for RT locks

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Add an rtlock_task pointer to rt_mutex_wake_q, which allows to handle the RT
specific wakeup for spin/rwlock waiters. The pointer is just consuming 4/8
bytes on the stack so it is provided unconditionaly to avoid #ifdeffery all
over the place.

This cannot use a regular wake_q, because a task can have concurrent wakeups which
would make it miss either lock or the regular wakeups, depending on what gets
queued first, unless task struct gains a separate wake_q_node for this, which
would be overkill, because there can only be a single task which gets woken
up in the spin/rw_lock unlock path.

No functional change for non-RT enabled kernels.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.253614678@linutronix.de
This commit is contained in:
Thomas Gleixner
2021-08-15 23:28:11 +02:00
committed by Ingo Molnar
parent 7980aa397c
commit 456cfbc65c
2 changed files with 20 additions and 3 deletions
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5
kernel/locking/rtmutex_common.h
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@@ -42,15 +42,18 @@ struct rt_mutex_waiter {
/**
* rt_wake_q_head - Wrapper around regular wake_q_head to support
* "sleeping" spinlocks on RT
* @head: The regular wake_q_head for sleeping lock variants
* @head: The regular wake_q_head for sleeping lock variants
* @rtlock_task: Task pointer for RT lock (spin/rwlock) wakeups
*/
struct rt_wake_q_head {
struct wake_q_head head;
struct task_struct *rtlock_task;
};
#define DEFINE_RT_WAKE_Q(name) \
struct rt_wake_q_head name = { \
.head = WAKE_Q_HEAD_INITIALIZER(name.head), \
.rtlock_task = NULL, \
}
/*