Messages in this thread Patch in this message | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH -mm 2/2] PM: Disable usermode helper before hibernation and suspend | Date | Sun, 17 Jun 2007 21:24:13 +0200 |
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On Friday, 15 June 2007 23:36, Rafael J. Wysocki wrote: > On Friday, 15 June 2007 15:08, Uli Luckas wrote: > > On Monday, 4. June 2007, Rafael J. Wysocki wrote: > > > From: Rafael J. Wysocki <rjw@sisk.pl> > > > > > > Use a hibernation and suspend notifier to disable the user mode helper > > > before a hibernation/suspend and enable it after the operation. > > > > > Hi Rafael, > > I have a couple of questions, regarding this patch ... > > > - if (!khelper_wq) > > > + if (!khelper_wq || usermodehelper_disabled) > > > return -EBUSY; > > 1) how about not returning -EBUSY here, if (wait == UMH_NO_WAIT)? > > Yes, this would make sense.
I know why I didn't do that from the start: my patch was against -rc4 and UMH_NO_WAIT is mm-only.
> > 2) how does your patch prevent wait_for_completion(&done) to hang during > > freezing if usermodehelper_pm_callback is called _after_ the above check? > > It doesn't. Once the helper is running, we can't distinguish it from any other > user land process. > > Still, it narrows the window quite a bit.
Okay, I think we can help it a bit. Please tell me what you think of the following patch (on top of 2.6.22-rc4-mm2).
Greetings, Rafael
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> --- kernel/kmod.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-)
Index: linux-2.6.22-rc4-mm2/kernel/kmod.c =================================================================== --- linux-2.6.22-rc4-mm2.orig/kernel/kmod.c +++ linux-2.6.22-rc4-mm2/kernel/kmod.c @@ -49,6 +49,15 @@ static struct workqueue_struct *khelper_ */ static int usermodehelper_disabled; +/* Number of helpers running */ +static atomic_t running_helpers = ATOMIC_INIT(0); + +/* + * Time to wait for running_helpers to become zero before the setting of + * usermodehelper_disabled in usermodehelper_pm_callback() fails + */ +#define RUNNING_HELPERS_TIMEOUT (5 * HZ) + #ifdef CONFIG_KMOD /* @@ -279,11 +288,20 @@ static int usermodehelper_pm_callback(st unsigned long action, void *ignored) { + DECLARE_WAIT_QUEUE_HEAD_ONSTACK(waiting); + switch (action) { case PM_HIBERNATION_PREPARE: case PM_SUSPEND_PREPARE: usermodehelper_disabled = 1; - return NOTIFY_OK; + wait_event_timeout(waiting, atomic_read(&running_helpers) == 0, + RUNNING_HELPERS_TIMEOUT); + if (atomic_read(&running_helpers) == 0) { + return NOTIFY_OK; + } else { + usermodehelper_disabled = 0; + return NOTIFY_BAD; + } case PM_POST_HIBERNATION: case PM_POST_SUSPEND: usermodehelper_disabled = 0; @@ -397,12 +415,13 @@ int call_usermodehelper_exec(struct subp DECLARE_COMPLETION_ONSTACK(done); int retval; + atomic_inc(&running_helpers); if (sub_info->path[0] == '\0') { retval = 0; goto out; } - if (!khelper_wq || usermodehelper_disabled) { + if (!khelper_wq || (wait != UMH_NO_WAIT && usermodehelper_disabled)) { retval = -EBUSY; goto out; } @@ -418,6 +437,7 @@ int call_usermodehelper_exec(struct subp out: call_usermodehelper_freeinfo(sub_info); + atomic_dec(&running_helpers); return retval; } EXPORT_SYMBOL(call_usermodehelper_exec); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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