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authorAndrew Morton <akpm@linux-foundation.org>2009-04-09 09:50:37 -0600
committerRusty Russell <rusty@rustcorp.com.au>2009-04-09 09:50:37 +0930
commit6b44003e5ca66a3fffeb5bc90f40ada2c4340896 (patch)
treed9dce0a39b5e66d8e760344a51ffb6de9594cd2f
parent1c99315bb36b5d776210546d438ca928dc9b1f22 (diff)
work_on_cpu(): rewrite it to create a kernel thread on demand
Impact: circular locking bugfix The various implemetnations and proposed implemetnations of work_on_cpu() are vulnerable to various deadlocks because they all used queues of some form. Unrelated pieces of kernel code thus gained dependencies wherein if one work_on_cpu() caller holds a lock which some other work_on_cpu() callback also takes, the kernel could rarely deadlock. Fix this by creating a short-lived kernel thread for each work_on_cpu() invokation. This is not terribly fast, but the only current caller of work_on_cpu() is pci_call_probe(). It would be nice to find some other way of doing the node-local allocations in the PCI probe code so that we can zap work_on_cpu() altogether. The code there is rather nasty. I can't think of anything simple at this time... Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r--kernel/workqueue.c36
1 files changed, 19 insertions, 17 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index b6b966ce145..f71fb2a0895 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -966,20 +966,20 @@ undo:
}
#ifdef CONFIG_SMP
-static struct workqueue_struct *work_on_cpu_wq __read_mostly;
struct work_for_cpu {
- struct work_struct work;
+ struct completion completion;
long (*fn)(void *);
void *arg;
long ret;
};
-static void do_work_for_cpu(struct work_struct *w)
+static int do_work_for_cpu(void *_wfc)
{
- struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work);
-
+ struct work_for_cpu *wfc = _wfc;
wfc->ret = wfc->fn(wfc->arg);
+ complete(&wfc->completion);
+ return 0;
}
/**
@@ -990,17 +990,23 @@ static void do_work_for_cpu(struct work_struct *w)
*
* This will return the value @fn returns.
* It is up to the caller to ensure that the cpu doesn't go offline.
+ * The caller must not hold any locks which would prevent @fn from completing.
*/
long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
{
- struct work_for_cpu wfc;
-
- INIT_WORK(&wfc.work, do_work_for_cpu);
- wfc.fn = fn;
- wfc.arg = arg;
- queue_work_on(cpu, work_on_cpu_wq, &wfc.work);
- flush_work(&wfc.work);
-
+ struct task_struct *sub_thread;
+ struct work_for_cpu wfc = {
+ .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
+ .fn = fn,
+ .arg = arg,
+ };
+
+ sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
+ if (IS_ERR(sub_thread))
+ return PTR_ERR(sub_thread);
+ kthread_bind(sub_thread, cpu);
+ wake_up_process(sub_thread);
+ wait_for_completion(&wfc.completion);
return wfc.ret;
}
EXPORT_SYMBOL_GPL(work_on_cpu);
@@ -1016,8 +1022,4 @@ void __init init_workqueues(void)
hotcpu_notifier(workqueue_cpu_callback, 0);
keventd_wq = create_workqueue("events");
BUG_ON(!keventd_wq);
-#ifdef CONFIG_SMP
- work_on_cpu_wq = create_workqueue("work_on_cpu");
- BUG_ON(!work_on_cpu_wq);
-#endif
}