| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20090318042219.29196DDF4E@ozlabs.org>
Date: Wed, 18 Mar 2009 10:40:24 +1030
From: Rusty Russell <rusty@...tcorp.com.au>
To: linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 1/9] work_on_cpu(): rewrite it to create a kernel thread on demand
From: Andrew Morton <akpm@...ux-foundation.org>
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: Rusty Russell <rusty@...tcorp.com.au>
Cc: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
---
kernel/workqueue.c | 36 +++++++++++++++++++-----------------
1 file changed, 19 insertions(+), 17 deletions(-)
diff -puN kernel/workqueue.c~work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand kernel/workqueue.c
--- a/kernel/workqueue.c~work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand
+++ a/kernel/workqueue.c
@@ -985,20 +985,20 @@ 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;
}
/**
@@ -1009,17 +1009,23 @@ static void do_work_for_cpu(struct work_
*
* 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);
@@ -1035,8 +1041,4 @@ 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
}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists