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authorDavidlohr Bueso <dave@stgolabs.net>2020-04-24 08:48:35 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2020-05-13 19:14:53 +0300
commit5c21f7b322cb9fcb97f2e22f5976a0ae8dd71354 (patch)
tree72ec9240d0723c39b70672ccfc1c63a33b4fd094 /include/linux/rcuwait.h
parent9d9a6ebfea329cadeda87544dceae01e9c27aaef (diff)
downloadlinux-5c21f7b322cb9fcb97f2e22f5976a0ae8dd71354.tar.xz
rcuwait: Introduce prepare_to and finish_rcuwait
This allows further flexibility for some callers to implement ad-hoc versions of the generic rcuwait_wait_event(). For example, kvm will need this to maintain tracing semantics. The naming is of course similar to what waitqueue apis offer. Also go ahead and make use of rcu_assign_pointer() for both task writes as it will make the __rcu sparse people happy - this will be the special nil case, thus no added serialization. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Message-Id: <20200424054837.5138-4-dave@stgolabs.net> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'include/linux/rcuwait.h')
-rw-r--r--include/linux/rcuwait.h21
1 files changed, 16 insertions, 5 deletions
diff --git a/include/linux/rcuwait.h b/include/linux/rcuwait.h
index 6ebb23258a27..45bc6604e9b1 100644
--- a/include/linux/rcuwait.h
+++ b/include/linux/rcuwait.h
@@ -29,12 +29,25 @@ extern int rcuwait_wake_up(struct rcuwait *w);
/*
* 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.
*/
+
+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; \
- rcu_assign_pointer((w)->task, current); \
+ prepare_to_rcuwait(w); \
for (;;) { \
/* \
* Implicit barrier (A) pairs with (B) in \
@@ -51,9 +64,7 @@ extern int rcuwait_wake_up(struct rcuwait *w);
\
schedule(); \
} \
- \
- WRITE_ONCE((w)->task, NULL); \
- __set_current_state(TASK_RUNNING); \
+ finish_rcuwait(w); \
__ret; \
})