Module Name: src
Committed By: riastradh
Date: Sun Dec 19 12:38:56 UTC 2021
Modified Files:
src/sys/external/bsd/drm2/linux: linux_kthread.c
Log Message:
linux: In kthread_park, wake thread to re-check kthread_shouldpark.
Otherwise, the thread to pakr may be sleeping on some condvar not
noticing it has to notify kthread_park --> deadlock.
To generate a diff of this commit:
cvs rdiff -u -r1.3 -r1.4 src/sys/external/bsd/drm2/linux/linux_kthread.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/external/bsd/drm2/linux/linux_kthread.c
diff -u src/sys/external/bsd/drm2/linux/linux_kthread.c:1.3 src/sys/external/bsd/drm2/linux/linux_kthread.c:1.4
--- src/sys/external/bsd/drm2/linux/linux_kthread.c:1.3 Sun Dec 19 12:29:39 2021
+++ src/sys/external/bsd/drm2/linux/linux_kthread.c Sun Dec 19 12:38:56 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: linux_kthread.c,v 1.3 2021/12/19 12:29:39 riastradh Exp $ */
+/* $NetBSD: linux_kthread.c,v 1.4 2021/12/19 12:38:56 riastradh Exp $ */
/*-
* Copyright (c) 2021 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_kthread.c,v 1.3 2021/12/19 12:29:39 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_kthread.c,v 1.4 2021/12/19 12:38:56 riastradh Exp $");
#include <sys/types.h>
@@ -184,13 +184,46 @@ kthread_should_stop(void)
void
kthread_park(struct task_struct *T)
{
+ struct lwp *l;
mutex_enter(&T->kt_lock);
+
+ /* Caller must not ask to park if they've already asked to stop. */
KASSERT(!T->kt_shouldstop);
+
+ /* Ask the thread to park. */
T->kt_shouldpark = true;
+
+ /* Don't wait for ourselves -- Linux allows this semantics. */
+ if ((l = T->kt_lwp) == curlwp)
+ goto out;
+
+ /*
+ * If the thread is asleep for any reason, give it a spurious
+ * wakeup. The thread is responsible for checking
+ * kthread_shouldpark before sleeping. This logic is like
+ * sleepq_timeout, but without setting LW_STIMO.
+ */
+ lwp_lock(l);
+ if (l->l_wchan == NULL) {
+ /*
+ * Not sleeping, so no need to wake up -- the thread
+ * will eventually check kthread_shouldpark.
+ */
+ lwp_unlock(l);
+ } else {
+ /*
+ * Sleeping, so wake it up. lwp_unsleep has the side
+ * effect of unlocking l when we pass unlock=true.
+ */
+ lwp_unsleep(l, /*unlock*/true);
+ }
+
+ /* Wait until the thread has issued kthread_parkme. */
while (!T->kt_parked)
cv_wait(&T->kt_cv, &T->kt_lock);
- mutex_exit(&T->kt_lock);
+
+out: mutex_exit(&T->kt_lock);
}
void
