Re: Soft lockup in e100 driver ?

[Matti Aarnio <matti.aarnio@zmailer.org>]

On Tue, Aug 09, 2005 at 09:16:21AM -0700, Daniel Walker wrote:
> It looks like this might be an SMP race , it seem that both processors
> are in e100_down(). There is a while loop in e100_clean_cbs() that
> appears to have an unsafe looping condition . 
> 
> It looks like cbs_avail might jump over params.cbs.count , then you
> would have to wait for a rollover . Is this a PREEMPT_NONE kernel?

  # CONFIG_PREEMPT is not set
  # CONFIG_PREEMPT_BKL is not set

which is probably same as "NONE".

There is _one_ processor in down, but other may be in trying to send
some data out, or otherwise polling the card.

However...  while real bugs in their own sense, none of these are
as important as original "card dies" thing, during a recovery of
which all this soft-lockup merryment happens.

Also, as it happens only once a week or so (except when it happens
right after another), testing code patches is rather slow.
I can guess which things make it more likely, but I can't make it
happen at will.

  /Matti Aarnio


> This patch may help, but it's not a complete fix.
> 
> --- linux-2.6.12.orig/drivers/net/e100.c        2005-08-05 16:45:59.000000000 +0000
> +++ linux-2.6.12/drivers/net/e100.c     2005-08-09 16:14:45.000000000 +0000
> @@ -1393,7 +1393,7 @@ static inline int e100_tx_clean(struct n
>  static void e100_clean_cbs(struct nic *nic)
>  {
>         if(nic->cbs) {
> -               while(nic->cbs_avail != nic->params.cbs.count) {
> +               while(nic->cbs_avail < nic->params.cbs.count) {
>                         struct cb *cb = nic->cb_to_clean;
>                         if(cb->skb) {
>                                 pci_unmap_single(nic->pdev,
> 
> 
> 
> On Tue, 2005-08-09 at 16:36 +0300, Matti Aarnio wrote:
> > Running very recent Fedora Core Development kernel I can following
> > soft-oops..   ( 2.6.12-1.1455_FC5smp )
> > 
> > 
> > e100: eth0: e100_watchdog: link up, 100Mbps, full-duplex
> > BUG: soft lockup detected on CPU#0!
> > 
> > Pid: 10743, comm:             ifconfig
> > EIP: 0060:[<f88bf2f9>] CPU: 0
> > EIP is at e100_clean_cbs+0x2f/0x12b [e100]
> >  EFLAGS: 00000293    Not tainted  (2.6.12-1.1455_FC5smp)
> > EAX: 495c7c2b EBX: 495c7c2b ECX: f6c311a0 EDX: 00000000
> > ESI: 00000040 EDI: f6c30000 EBP: f71a4b20 DS: 007b ES: 007b
> > CR0: 8005003b CR2: 0804a544 CR3: 01e9cd80 CR4: 000006f0
> >  [<f88c0708>] e100_down+0x66/0x9a [e100]
> >  [<f88c1623>] e100_close+0xa/0xd [e100]
> >  [<c02b7adb>] dev_close+0x40/0x7e
> >  [<c02b8f59>] dev_change_flags+0x46/0xf5
> >  [<c02f76b3>] devinet_ioctl+0x564/0x5df
> >  [<c02af22c>] sock_ioctl+0xc3/0x250
> >  [<c02af169>] sock_ioctl+0x0/0x250
> >  [<c01762ef>] do_ioctl+0x1f/0x6d
> >  [<c017648f>] vfs_ioctl+0x50/0x1c6
> >  [<c0176662>] sys_ioctl+0x5d/0x6f
> >  [<c010394d>] syscall_call+0x7/0xb
> >  [<c014473f>] softlockup_tick+0x6f/0x80
> >  [<c01085b8>] timer_interrupt+0x2d/0x75
> >  [<c01448dd>] handle_IRQ_event+0x2e/0x5a
> >  [<c01449cb>] __do_IRQ+0xc2/0x127
> >  [<c0105f7e>] do_IRQ+0x4e/0x86
> >  =======================
> >  [<c01160cc>] smp_apic_timer_interrupt+0xc1/0xca
> >  [<c0104382>] common_interrupt+0x1a/0x20
> >  [<f88bf2f9>] e100_clean_cbs+0x2f/0x12b [e100]
> >  [<f88c0708>] e100_down+0x66/0x9a [e100]
> >  [<f88c1623>] e100_close+0xa/0xd [e100]
> >  [<c02b7adb>] dev_close+0x40/0x7e
> >  [<c02b8f59>] dev_change_flags+0x46/0xf5
> >  [<c02f76b3>] devinet_ioctl+0x564/0x5df
> >  [<c02af22c>] sock_ioctl+0xc3/0x250
> >  [<c02af169>] sock_ioctl+0x0/0x250
> >  [<c01762ef>] do_ioctl+0x1f/0x6d
> >  [<c017648f>] vfs_ioctl+0x50/0x1c6
> >  [<c0176662>] sys_ioctl+0x5d/0x6f
> >  [<c010394d>] syscall_call+0x7/0xb
> > 
> > 
> > 
> > Preconditions for this are:
> > 
> > - E100 card stopped working for some reason (no idea why, it just
> >   does sometimes at this oldish 2x P-III machine)
> > - There are active datastreams running in and out
> >   (around 0.2 Mbps out, multiple megabits in.)
> > - Commanding then "ifconfig eth0 down" results in what feels like 
> >   system freezing, but it does recover in about 30-60 seconds
> >   (it takes long enough for me to sweat bullets...)
> > - While in freeze state, keyboard can go crazy, but mouse does
> >   respond, as well as tvtime shows bt848 captured live video.
> > -
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