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Message-Id: <20221024104425.16423-8-wagi@monom.org>
Date: Mon, 24 Oct 2022 12:44:23 +0200
From: Daniel Wagner <wagi@...om.org>
To: LKML <linux-kernel@...r.kernel.org>,
linux-rt-users <linux-rt-users@...r.kernel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
Carsten Emde <C.Emde@...dl.org>,
John Kacur <jkacur@...hat.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Tom Zanussi <tom.zanussi@...ux.intel.com>,
Clark Williams <williams@...hat.com>,
Pavel Machek <pavel@...x.de>
Cc: Daniel Wagner <wagi@...om.org>
Subject: [PATCH RT 7/9] rcu: Update rcuwait
v4.19.255-rt114-rc1 stable review patch.
If anyone has any objections, please let me know.
-----------
This is an all in one commit backporting updates for rcuwait:
- 03f4b48edae7 ("rcuwait: Annotate task_struct with __rcu")
- 191a43be61d6 ("rcuwait: Introduce rcuwait_active()")
- 5c21f7b322cb ("rcuwait: Introduce prepare_to and finish_rcuwait")
- 80fbaf1c3f29 ("rcuwait: Add @state argument to rcuwait_wait_event()")
- 9d9a6ebfea32 ("rcuwait: Let rcuwait_wake_up() return whether or not a task was awoken")
- 58d4292bd037 ("rcu: Uninline multi-use function: finish_rcuwait()")
Signed-off-by: Daniel Wagner <wagi@...om.org>
---
include/linux/rcuwait.h | 42 +++++++++++++++++++++++++++--------
kernel/exit.c | 7 ++++--
kernel/locking/percpu-rwsem.c | 2 +-
kernel/rcu/update.c | 8 +++++++
4 files changed, 47 insertions(+), 12 deletions(-)
diff --git a/include/linux/rcuwait.h b/include/linux/rcuwait.h
index 90bfa3279a01..4fe9ecd56aac 100644
--- a/include/linux/rcuwait.h
+++ b/include/linux/rcuwait.h
@@ -3,6 +3,7 @@
#define _LINUX_RCUWAIT_H_
#include <linux/rcupdate.h>
+#include <linux/sched/signal.h>
/*
* rcuwait provides a way of blocking and waking up a single
@@ -18,7 +19,7 @@
* awoken.
*/
struct rcuwait {
- struct task_struct *task;
+ struct task_struct __rcu *task;
};
#define __RCUWAIT_INITIALIZER(name) \
@@ -29,14 +30,33 @@ static inline void rcuwait_init(struct rcuwait *w)
w->task = NULL;
}
-extern void rcuwait_wake_up(struct rcuwait *w);
+extern int rcuwait_wake_up(struct rcuwait *w);
+
+/*
+ * 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);
+}
/*
* The caller is responsible for locking around rcuwait_wait_event(),
- * such that writes to @task are properly serialized.
+ * and [prepare_to/finish]_rcuwait() such that writes to @task are
+ * properly serialized.
*/
-#define rcuwait_wait_event(w, condition) \
+
+static inline void prepare_to_rcuwait(struct rcuwait *w)
+{
+ rcu_assign_pointer(w->task, current);
+}
+
+extern void finish_rcuwait(struct rcuwait *w);
+
+#define rcuwait_wait_event(w, condition, state) \
({ \
+ int __ret = 0; \
/* \
* Complain if we are called after do_exit()/exit_notify(), \
* as we cannot rely on the rcu critical region for the \
@@ -44,21 +64,25 @@ extern void rcuwait_wake_up(struct rcuwait *w);
*/ \
WARN_ON(current->exit_state); \
\
- rcu_assign_pointer((w)->task, current); \
+ prepare_to_rcuwait(w); \
for (;;) { \
/* \
* Implicit barrier (A) pairs with (B) in \
* rcuwait_wake_up(). \
*/ \
- set_current_state(TASK_UNINTERRUPTIBLE); \
+ set_current_state(state); \
if (condition) \
break; \
\
+ if (signal_pending_state(state, current)) { \
+ __ret = -EINTR; \
+ break; \
+ } \
+ \
schedule(); \
} \
- \
- WRITE_ONCE((w)->task, NULL); \
- __set_current_state(TASK_RUNNING); \
+ finish_rcuwait(w); \
+ __ret; \
})
#endif /* _LINUX_RCUWAIT_H_ */
diff --git a/kernel/exit.c b/kernel/exit.c
index 2a414fc71b87..cf68896a94fa 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -291,8 +291,9 @@ struct task_struct *task_rcu_dereference(struct task_struct **ptask)
return task;
}
-void rcuwait_wake_up(struct rcuwait *w)
+int rcuwait_wake_up(struct rcuwait *w)
{
+ int ret = 0;
struct task_struct *task;
rcu_read_lock();
@@ -316,8 +317,10 @@ void rcuwait_wake_up(struct rcuwait *w)
*/
task = rcu_dereference(w->task);
if (task)
- wake_up_process(task);
+ ret = wake_up_process(task);
rcu_read_unlock();
+
+ return ret;
}
/*
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 883cf1b92d90..41787e80dbde 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -159,7 +159,7 @@ void percpu_down_write(struct percpu_rw_semaphore *sem)
*/
/* Wait for all now active readers to complete. */
- rcuwait_wait_event(&sem->writer, readers_active_check(sem));
+ rcuwait_wait_event(&sem->writer, readers_active_check(sem), TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL_GPL(percpu_down_write);
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index ed75addd3ccd..4b2ce6bb94a4 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -53,6 +53,7 @@
#include <linux/rcupdate_wait.h>
#include <linux/sched/isolation.h>
#include <linux/kprobes.h>
+#include <linux/rcuwait.h>
#define CREATE_TRACE_POINTS
@@ -375,6 +376,13 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
}
EXPORT_SYMBOL_GPL(__wait_rcu_gp);
+void finish_rcuwait(struct rcuwait *w)
+{
+ rcu_assign_pointer(w->task, NULL);
+ __set_current_state(TASK_RUNNING);
+}
+EXPORT_SYMBOL_GPL(finish_rcuwait);
+
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
void init_rcu_head(struct rcu_head *head)
{
--
2.38.0
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