Module Name: src
Committed By: riastradh
Date: Sat Jan 23 16:33:49 UTC 2021
Modified Files:
src/sys/kern: kern_threadpool.c
Log Message:
threadpool(9): Fix synchronization between cancel and dispatch.
- threadpool_cancel_job_async tried to prevent
threadpool_dispatcher_thread from taking the job by setting
job->job_thread = NULL and then removing the job from the queue.
- But threadpool_cancel_job_async didn't notice job->job_thread is
null until after it also removes the job from the queue =>
double-remove, *boom*.
The solution is to teach threadpool_dispatcher_thread to wait until
it has acquired the job lock to test whether job->job_thread is still
valid before it decides to remove the job from the queue.
Fixes PR kern/55948.
XXX pullup-9
To generate a diff of this commit:
cvs rdiff -u -r1.22 -r1.23 src/sys/kern/kern_threadpool.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/kern/kern_threadpool.c
diff -u src/sys/kern/kern_threadpool.c:1.22 src/sys/kern/kern_threadpool.c:1.23
--- src/sys/kern/kern_threadpool.c:1.22 Wed Jan 13 07:34:37 2021
+++ src/sys/kern/kern_threadpool.c Sat Jan 23 16:33:49 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_threadpool.c,v 1.22 2021/01/13 07:34:37 skrll Exp $ */
+/* $NetBSD: kern_threadpool.c,v 1.23 2021/01/23 16:33:49 riastradh Exp $ */
/*-
* Copyright (c) 2014, 2018 The NetBSD Foundation, Inc.
@@ -81,7 +81,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_threadpool.c,v 1.22 2021/01/13 07:34:37 skrll Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_threadpool.c,v 1.23 2021/01/23 16:33:49 riastradh Exp $");
#include <sys/types.h>
#include <sys/param.h>
@@ -1041,7 +1041,7 @@ threadpool_dispatcher_thread(void *arg)
/* There are idle threads, so try giving one a job. */
struct threadpool_job *const job = TAILQ_FIRST(&pool->tp_jobs);
- TAILQ_REMOVE(&pool->tp_jobs, job, job_entry);
+
/*
* Take an extra reference on the job temporarily so that
* it won't disappear on us while we have both locks dropped.
@@ -1053,6 +1053,7 @@ threadpool_dispatcher_thread(void *arg)
/* If the job was cancelled, we'll no longer be its thread. */
if (__predict_true(job->job_thread == dispatcher)) {
mutex_spin_enter(&pool->tp_lock);
+ TAILQ_REMOVE(&pool->tp_jobs, job, job_entry);
if (__predict_false(
TAILQ_EMPTY(&pool->tp_idle_threads))) {
/*
