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SubjectRe: 2.6.35->2.6.36 regression, vanilla kernel panic, ppp or hrtimers crashing
On Wed, Nov 03, 2010 at 10:18:20AM +0200, Denys Fedoryshchenko wrote:
>
> On Wednesday 03 November 2010 10:02:58 Jarek Poplawski wrote:
> > On Wed, Nov 03, 2010 at 09:47:53AM +0200, Denys Fedoryshchenko wrote:
> > > I try to reverse and got very weird lockups (no netconsole logs and no
> > > watchdog triggered reboot on that remote machine).
> > > I will try to cook something to reboot it, because it is very remote
> > > machine
> >
> > OK, I only wanted to know if reverting could be a fast fix. Since it
> > isn't, please stay with 2.6.35 until there is some new idea (patch).
> >
> Well, still i want to try (if i can) more debug, and maybe i'll catch
> something, also i have around 145 NAS servers to go, to try 2.6.36 :-)

I think the current debugging needs analyzing first. But here is
a patch which probably could matter at least wrt your first oopses.
(Please try this first on something you can easily reboot.)

Jarek P.
---
diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 09cf56d..1b98c4c 100644
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -409,6 +409,8 @@ static ssize_t ppp_read(struct file *file, char __user *buf,

if (!pf)
return -ENXIO;
+
+ atomic_inc(&pf->refcnt);
add_wait_queue(&pf->rwait, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
@@ -440,6 +442,17 @@ static ssize_t ppp_read(struct file *file, char __user *buf,
set_current_state(TASK_RUNNING);
remove_wait_queue(&pf->rwait, &wait);

+ if (atomic_dec_and_test(&pf->refcnt)) {
+ switch (pf->kind) {
+ case INTERFACE:
+ ppp_destroy_interface(PF_TO_PPP(pf));
+ break;
+ case CHANNEL:
+ ppp_destroy_channel(PF_TO_CHANNEL(pf));
+ break;
+ }
+ }
+
if (!skb)
goto out;

@@ -504,6 +517,8 @@ static unsigned int ppp_poll(struct file *file, poll_table *wait)

if (!pf)
return 0;
+
+ atomic_inc(&pf->refcnt);
poll_wait(file, &pf->rwait, wait);
mask = POLLOUT | POLLWRNORM;
if (skb_peek(&pf->rq))
@@ -518,6 +533,17 @@ static unsigned int ppp_poll(struct file *file, poll_table *wait)
mask |= POLLIN | POLLRDNORM;
}

+ if (atomic_dec_and_test(&pf->refcnt)) {
+ switch (pf->kind) {
+ case INTERFACE:
+ ppp_destroy_interface(PF_TO_PPP(pf));
+ break;
+ case CHANNEL:
+ ppp_destroy_channel(PF_TO_CHANNEL(pf));
+ break;
+ }
+ }
+
return mask;
}


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