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Message-Id: <200904091022.56550.rusty@rustcorp.com.au>
Date: Thu, 9 Apr 2009 10:22:56 +0930
From: Rusty Russell <rusty@...tcorp.com.au>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Vitaliy Gusev <vgusev@...nvz.org>,
Oleg Nesterov <oleg@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>
Subject: [PULL] kthread changes
The following changes since commit 7b85a88ca7760d6d5f34bdaa793c71d921a3e853:
Linus Torvalds (1):
Merge branch 'release' of git://git.kernel.org/.../lenb/linux-acpi-2.6
are available in the git repository at:
ssh://master.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus.git master
Andrew Morton (1):
work_on_cpu(): rewrite it to create a kernel thread on demand
Oleg Nesterov (1):
kthread: move sched-realeted initialization from kthreadd context
Vitaliy Gusev (1):
kthread: Don't looking for a task in create_kthread() #2
kernel/kthread.c | 26 ++++++++++++--------------
kernel/workqueue.c | 36 +++++++++++++++++++-----------------
2 files changed, 31 insertions(+), 31 deletions(-)
commit 3217ab97f14c5c8f9f975ed8c40c351164b0b10e
Author: Vitaliy Gusev <vgusev@...nvz.org>
Date: Thu Apr 9 09:50:35 2009 -0600
kthread: Don't looking for a task in create_kthread() #2
Remove the unnecessary find_task_by_pid_ns(). kthread() can just
use "current" to get the same result.
Signed-off-by: Vitaliy Gusev <vgusev@...nvz.org>
Acked-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
kernel/kthread.c | 4 +---
1 files changed, 1 insertions(+), 3 deletions(-)
commit 1c99315bb36b5d776210546d438ca928dc9b1f22
Author: Oleg Nesterov <oleg@...hat.com>
Date: Thu Apr 9 09:50:36 2009 -0600
kthread: move sched-realeted initialization from kthreadd context
kthreadd is the single thread which implements ths "create" request, move
sched_setscheduler/etc from create_kthread() to kthread_create() to
improve the scalability.
We should be careful with sched_setscheduler(), use _nochek helper.
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Cc: Christoph Hellwig <hch@....de>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Pavel Emelyanov <xemul@...nvz.org>
Cc: Vitaliy Gusev <vgusev@...nvz.org
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
kernel/kthread.c | 22 +++++++++++-----------
1 files changed, 11 insertions(+), 11 deletions(-)
commit 6b44003e5ca66a3fffeb5bc90f40ada2c4340896
Author: Andrew Morton <akpm@...ux-foundation.org>
Date: Thu Apr 9 09:50:37 2009 -0600
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@...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 files changed, 19 insertions(+), 17 deletions(-)
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 84bbadd..4ebaf85 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -76,6 +76,7 @@ static int kthread(void *_create)
/* OK, tell user we're spawned, wait for stop or wakeup */
__set_current_state(TASK_UNINTERRUPTIBLE);
+ create->result = current;
complete(&create->started);
schedule();
@@ -96,22 +97,10 @@ static void create_kthread(struct kthread_create_info *create)
/* We want our own signal handler (we take no signals by default). */
pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
- if (pid < 0) {
+ if (pid < 0)
create->result = ERR_PTR(pid);
- } else {
- struct sched_param param = { .sched_priority = 0 };
+ else
wait_for_completion(&create->started);
- read_lock(&tasklist_lock);
- create->result = find_task_by_pid_ns(pid, &init_pid_ns);
- read_unlock(&tasklist_lock);
- /*
- * root may have changed our (kthreadd's) priority or CPU mask.
- * The kernel thread should not inherit these properties.
- */
- sched_setscheduler(create->result, SCHED_NORMAL, ¶m);
- set_user_nice(create->result, KTHREAD_NICE_LEVEL);
- set_cpus_allowed_ptr(create->result, cpu_all_mask);
- }
complete(&create->done);
}
@@ -154,11 +143,20 @@ struct task_struct *kthread_create(int (*threadfn)(void *data),
wait_for_completion(&create.done);
if (!IS_ERR(create.result)) {
+ struct sched_param param = { .sched_priority = 0 };
va_list args;
+
va_start(args, namefmt);
vsnprintf(create.result->comm, sizeof(create.result->comm),
namefmt, args);
va_end(args);
+ /*
+ * root may have changed our (kthreadd's) priority or CPU mask.
+ * The kernel thread should not inherit these properties.
+ */
+ sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m);
+ set_user_nice(create.result, KTHREAD_NICE_LEVEL);
+ set_cpus_allowed_ptr(create.result, cpu_all_mask);
}
return create.result;
}
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
}
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