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 <[email protected]>
> > >
> > > 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 <[email protected]>
---
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 [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
