mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-15 23:26:39 +07:00
febd668d37
rcuwait_active only returns whether w->task is not NULL. This is exactly one of the usecases that are mentioned in the documentation for rcu_access_pointer() where it is correct to bypass lockdep checks. This avoids a splat from kvm_vcpu_on_spin(). Reported-by: Wanpeng Li <kernellwp@gmail.com> Tested-by: Wanpeng Li <kernellwp@gmail.com> Acked-by: Davidlohr Bueso <dave@stgolabs.net> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
81 lines
1.8 KiB
C
81 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _LINUX_RCUWAIT_H_
|
|
#define _LINUX_RCUWAIT_H_
|
|
|
|
#include <linux/rcupdate.h>
|
|
#include <linux/sched/signal.h>
|
|
|
|
/*
|
|
* rcuwait provides a way of blocking and waking up a single
|
|
* task in an rcu-safe manner.
|
|
*
|
|
* The only time @task is non-nil is when a user is blocked (or
|
|
* checking if it needs to) on a condition, and reset as soon as we
|
|
* know that the condition has succeeded and are awoken.
|
|
*/
|
|
struct rcuwait {
|
|
struct task_struct __rcu *task;
|
|
};
|
|
|
|
#define __RCUWAIT_INITIALIZER(name) \
|
|
{ .task = NULL, }
|
|
|
|
static inline void rcuwait_init(struct rcuwait *w)
|
|
{
|
|
w->task = NULL;
|
|
}
|
|
|
|
/*
|
|
* Note: this provides no serialization and, just as with waitqueues,
|
|
* requires care to estimate as to whether or not the wait is active.
|
|
*/
|
|
static inline int rcuwait_active(struct rcuwait *w)
|
|
{
|
|
return !!rcu_access_pointer(w->task);
|
|
}
|
|
|
|
extern int rcuwait_wake_up(struct rcuwait *w);
|
|
|
|
/*
|
|
* The caller is responsible for locking around rcuwait_wait_event(),
|
|
* and [prepare_to/finish]_rcuwait() such that writes to @task are
|
|
* properly serialized.
|
|
*/
|
|
|
|
static inline void prepare_to_rcuwait(struct rcuwait *w)
|
|
{
|
|
rcu_assign_pointer(w->task, current);
|
|
}
|
|
|
|
static inline void finish_rcuwait(struct rcuwait *w)
|
|
{
|
|
rcu_assign_pointer(w->task, NULL);
|
|
__set_current_state(TASK_RUNNING);
|
|
}
|
|
|
|
#define rcuwait_wait_event(w, condition, state) \
|
|
({ \
|
|
int __ret = 0; \
|
|
prepare_to_rcuwait(w); \
|
|
for (;;) { \
|
|
/* \
|
|
* Implicit barrier (A) pairs with (B) in \
|
|
* rcuwait_wake_up(). \
|
|
*/ \
|
|
set_current_state(state); \
|
|
if (condition) \
|
|
break; \
|
|
\
|
|
if (signal_pending_state(state, current)) { \
|
|
__ret = -EINTR; \
|
|
break; \
|
|
} \
|
|
\
|
|
schedule(); \
|
|
} \
|
|
finish_rcuwait(w); \
|
|
__ret; \
|
|
})
|
|
|
|
#endif /* _LINUX_RCUWAIT_H_ */
|