Commit 34c37b86 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds

[PATCH] workqueue.c subtle fix and core extraction

From: Rusty Russell <rusty@rustcorp.com.au>

A barrier is needed on workqueue shutdown: there's a chance that the thead
could see the wq->thread set to NULL before the completion is initialized.

Also extracts functions which actually create and destroy workqueues, for
use by hotplug CPU patch.
parent eebef30c
......@@ -259,24 +259,13 @@ void flush_workqueue(struct workqueue_struct *wq)
}
}
struct workqueue_struct *create_workqueue(const char *name)
static int create_workqueue_thread(struct workqueue_struct *wq,
const char *name,
int cpu)
{
int ret, cpu, destroy = 0;
struct cpu_workqueue_struct *cwq;
startup_t startup;
struct workqueue_struct *wq;
BUG_ON(strlen(name) > 10);
startup.name = name;
wq = kmalloc(sizeof(*wq), GFP_KERNEL);
if (!wq)
return NULL;
for (cpu = 0; cpu < NR_CPUS; cpu++) {
if (!cpu_online(cpu))
continue;
cwq = wq->cpu_wq + cpu;
struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
int ret;
spin_lock_init(&cwq->lock);
cwq->wq = wq;
......@@ -289,14 +278,31 @@ struct workqueue_struct *create_workqueue(const char *name)
init_completion(&startup.done);
startup.cwq = cwq;
ret = kernel_thread(worker_thread, &startup,
CLONE_FS | CLONE_FILES);
if (ret < 0)
destroy = 1;
else {
startup.name = name;
ret = kernel_thread(worker_thread, &startup, CLONE_FS | CLONE_FILES);
if (ret >= 0) {
wait_for_completion(&startup.done);
BUG_ON(!cwq->thread);
}
return ret;
}
struct workqueue_struct *create_workqueue(const char *name)
{
int cpu, destroy = 0;
struct workqueue_struct *wq;
BUG_ON(strlen(name) > 10);
wq = kmalloc(sizeof(*wq), GFP_KERNEL);
if (!wq)
return NULL;
for (cpu = 0; cpu < NR_CPUS; cpu++) {
if (!cpu_online(cpu))
continue;
if (create_workqueue_thread(wq, name, cpu) < 0)
destroy = 1;
}
/*
* Was there any error during startup? If yes then clean up:
......@@ -308,28 +314,33 @@ struct workqueue_struct *create_workqueue(const char *name)
return wq;
}
void destroy_workqueue(struct workqueue_struct *wq)
static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
{
struct cpu_workqueue_struct *cwq;
int cpu;
flush_workqueue(wq);
for (cpu = 0; cpu < NR_CPUS; cpu++) {
if (!cpu_online(cpu))
continue;
cwq = wq->cpu_wq + cpu;
if (!cwq->thread)
continue;
/*
* Initiate an exit and wait for it:
*/
if (cwq->thread) {
printk("Cleaning up workqueue thread for %i\n", cpu);
/* Initiate an exit and wait for it: */
init_completion(&cwq->exit);
wmb(); /* Thread must see !cwq->thread after completion init */
cwq->thread = NULL;
wake_up(&cwq->more_work);
wait_for_completion(&cwq->exit);
}
}
void destroy_workqueue(struct workqueue_struct *wq)
{
int cpu;
flush_workqueue(wq);
for (cpu = 0; cpu < NR_CPUS; cpu++) {
if (cpu_online(cpu))
cleanup_workqueue_thread(wq, cpu);
}
kfree(wq);
}
......
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