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author | Andrew Morton <akpm@linux-foundation.org> | 2009-04-09 09:50:37 -0600 |
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committer | Rusty Russell <rusty@rustcorp.com.au> | 2009-04-09 09:50:37 +0930 |
commit | 6b44003e5ca66a3fffeb5bc90f40ada2c4340896 (patch) | |
tree | d9dce0a39b5e66d8e760344a51ffb6de9594cd2f /kernel | |
parent | 1c99315bb36b5d776210546d438ca928dc9b1f22 (diff) | |
download | op-kernel-dev-6b44003e5ca66a3fffeb5bc90f40ada2c4340896.zip op-kernel-dev-6b44003e5ca66a3fffeb5bc90f40ada2c4340896.tar.gz |
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>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/workqueue.c | 36 |
1 files changed, 19 insertions, 17 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index b6b966c..f71fb2a 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 } |