Re: 2.4.20: Proccess stuck in __lock_page ...

[Andrea Arcangeli]

On Tue, May 27, 2003 at 12:34:38PM -0700, manish wrote:
> Marcelo Tosatti wrote:
> 
> >
> >On Tue, 27 May 2003, manish wrote:
> >
> >>Marcelo Tosatti wrote:
> >>
> >>>On Tue, 27 May 2003, manish wrote:
> >>>
> >>>>Marc-Christian Petersen wrote:
> >>>>
> >>>>>On Tuesday 27 May 2003 20:33, Marcelo Tosatti wrote:
> >>>>>
> >>>>>Hi Marcelo,
> >>>>>
> >>>>>>It seems your "fix-pausing" patch is fixing a potential wakeup
> >>>>>>miss, right? (I looked quickly throught it). Could you explain me the
> >>>>>>problem its trying to fix and how?
> >>>>>>
> >>>>>Please have also a look here:
> >>>>>
> >>>>>http://hypermail.idiosynkrasia.net/linux-kernel/archived/2002/week45/0305.html
> >>>>>
> >>>>>ciao, Marc
> >>>>>
> >>>>Hello !
> >>>>
> >>>>I applied the fix-pausing-2 patch to the 2.4.20 kernel. This time on,
> >>>>the stack trace:
> >>>>
> >>>>sys_write
> >>>>generic_file_write
> >>>>ext2_get_group_desc
> >>>>bread
> >>>>__wait_on_buffer
> >>>>schedule
> >>>>
> >>>Huh? You mean bonnie still deadlocks or ?
> >>>
> >>At the time the processes get stuck:
> >>
> >>
> >>[root@dyn-10-123-130-235 vm]# more /proc/meminfo
> >>       total:    used:    free:  shared: buffers:  cached:
> >>Mem:  3709870080 3699126272 10743808        0 18313216 3531255808
> >>Swap: 1077501952        0 1077501952
> >>MemTotal:      3622920 kB
> >>MemFree:         10492 kB
> >>MemShared:           0 kB
> >>Buffers:         17884 kB
> >>Cached:        3448492 kB
> >>SwapCached:          0 kB
> >>Active:          25252 kB
> >>Inactive:      3445344 kB
> >>HighTotal:     2752512 kB
> >>HighFree:         2120 kB
> >>LowTotal:       870408 kB
> >>LowFree:          8372 kB
> >>SwapTotal:     1052248 kB
> >>SwapFree:      1052248 kB
> >>
> >
> >Ok, so just to confirm: You're still getting pauses with Andrea's patches
> >but no hangs anymore?
> >
> >Correct?
> >
> Hi Marcelo,
> 
> I have applied Andrea's patch to two kernels:
> 
> 1. Stock 2.4.20
> 2. 2.4.20 with the io_request_lock removed.
> 
> The tests on the first one are still going. The tests on the second one 
> showed processes getting stuck for long times (> 5 minutes) and not 
> paused ...

sorry if it's a dumb question but what is the "io_request_lock removed"
thing? Hope you didn't delete any io_request_lock, if you did you can
get worse things than crashes (i.e. mm/fs corruption). the pausing bug
was a genuine race (quite innocent, if you could trigger a disk unplug
you could recover from it)

Andrea