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authorDavid Gwynne <dlg@cvs.openbsd.org>2017-11-24 02:36:54 +0000
committerDavid Gwynne <dlg@cvs.openbsd.org>2017-11-24 02:36:54 +0000
commit8c8ca2984185a4971d1e2ba781ed9b1c266168b1 (patch)
treef6529c40d72bac8cd0232dabce88ac7ac2c8ae73 /sys
parent8f9817eee2dd2a01973e2a9a1b27d58c9900a4db (diff)
add timeout_barrier, which is like intr_barrier and taskq_barrier.
if you're trying to free something that a timeout is using, you have to wait for that timeout to finish running before doing the free. timeout_del can stop a timeout from running in the future, but it doesn't know if a timeout has finished being scheduled and is now running. previously you could know that timeouts are not running by simply masking softclock interrupts on the cpu running the kernel. however, code is now running outside the kernel lock, and timeouts can run in a thread instead of softclock. timeout_barrier solves the first problem by taking the kernel lock and then masking softclock interrupts. that is enough to ensure that any further timeout processing is waiting for those resources to run again. the second problem is solved by having timeout_barrier insert work into the thread. when that work runs, that means all previous work running in that thread has completed. fixes and ok visa@, who thinks this will be useful for his work too.
Diffstat (limited to 'sys')
-rw-r--r--sys/kern/kern_timeout.c42
-rw-r--r--sys/sys/timeout.h3
2 files changed, 43 insertions, 2 deletions
diff --git a/sys/kern/kern_timeout.c b/sys/kern/kern_timeout.c
index f3e2fe29c3d..00565e8a909 100644
--- a/sys/kern/kern_timeout.c
+++ b/sys/kern/kern_timeout.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kern_timeout.c,v 1.50 2016/10/03 11:54:29 dlg Exp $ */
+/* $OpenBSD: kern_timeout.c,v 1.51 2017/11/24 02:36:53 dlg Exp $ */
/*
* Copyright (c) 2001 Thomas Nordin <nordin@openbsd.org>
* Copyright (c) 2000-2001 Artur Grabowski <art@openbsd.org>
@@ -324,6 +324,46 @@ timeout_del(struct timeout *to)
return (ret);
}
+void timeout_proc_barrier(void *);
+
+void
+timeout_barrier(struct timeout *to)
+{
+ if (!ISSET(to->to_flags, TIMEOUT_NEEDPROCCTX)) {
+ KERNEL_LOCK();
+ splx(splsoftclock());
+ KERNEL_UNLOCK();
+ } else {
+ int wait = 1;
+ struct timeout barrier;
+ struct sleep_state sls;
+
+ timeout_set_proc(&barrier, timeout_proc_barrier, &wait);
+
+ mtx_enter(&timeout_mutex);
+ barrier.to_flags |= TIMEOUT_ONQUEUE;
+ CIRCQ_INSERT(&barrier.to_list, &timeout_proc);
+ mtx_leave(&timeout_mutex);
+
+ wakeup_one(&timeout_proc);
+
+ while (wait) {
+ sleep_setup(&sls, &wait, PSWP, "tmobar");
+ sleep_finish(&sls, wait);
+ }
+ }
+}
+
+void
+timeout_proc_barrier(void *arg)
+{
+ int *wait = arg;
+
+ *wait = 0;
+
+ wakeup_one(wait);
+}
+
/*
* This is called from hardclock() once every tick.
* We return !0 if we need to schedule a softclock.
diff --git a/sys/sys/timeout.h b/sys/sys/timeout.h
index a00c62058a1..9aaa4ffdf88 100644
--- a/sys/sys/timeout.h
+++ b/sys/sys/timeout.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: timeout.h,v 1.26 2016/09/22 12:55:24 mpi Exp $ */
+/* $OpenBSD: timeout.h,v 1.27 2017/11/24 02:36:53 dlg Exp $ */
/*
* Copyright (c) 2000-2001 Artur Grabowski <art@openbsd.org>
* All rights reserved.
@@ -99,6 +99,7 @@ int timeout_add_msec(struct timeout *, int);
int timeout_add_usec(struct timeout *, int);
int timeout_add_nsec(struct timeout *, int);
int timeout_del(struct timeout *);
+void timeout_barrier(struct timeout *);
void timeout_startup(void);
void timeout_adjust_ticks(int);