lkml.org 
[lkml]   [2007]   [Mar]   [21]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
    /
    From"Rafael J. Wysocki" <>
    SubjectRe: [BUG] Code reordering in swsusp breaks suspend on SMP systems
    DateWed, 21 Mar 2007 23:39:02 +0100
    On Wednesday, 21 March 2007 23:21, Pavel Machek wrote:
    > Hi!
    > 
    > > Starting with 2.6.21-rc1 suspend to ram and disk doesn't work anymore on my system.
    > > 
    > > I did a git-bisect and found that those commits break it:
    > > 
    > > e3c7db621bed4afb8e231cb005057f2feb5db557 - [PATCH] [PATCH] PM: Change code ordering in main.c
    > > ed746e3b18f4df18afa3763155972c5835f284c5 - [PATCH] [PATCH] swsusp: Change code ordering in disk.c
    > > 259130526c267550bc365d3015917d90667732f1 - [PATCH] [PATCH] swsusp: Change code ordering in user.c
    > > 
    > 
    > (Yep, it was in my "to analyze" queue).
    > 
    > > I already reported about it, but now i know the reason why suspend breaks.
    > > 
    > > The problem is that both cpu_up/cpu_down were allowed to sleep until now, 
    > > and it did work because those functions could be called only in process context
    > > (the one that writes to /sys/devices/system/cpu/cpu*/online) or  idle thread  that does smp_init()).
    > > 
    > > But now they are called _after_ all tasks were suspended, so if cpu_down tries for example to take a lock
    > > that is taken by different process, it can't since the different proccess is frozen and can't release the lock.
    > > 
    > 
    > Thanks for detailed explanation.
    > 
    > ...but, on my machine suspend works ok in -rc4. I'm not seeing this.
    > 
    > ...by design, "frozen" tasks must not hold any locks. If frozen task
    > holds a lock, that's a bug.
    > 
    > > Or, it is also possible to revert this change.
    > 
    > Are you using xfs?
    
    Well, this is the only case that can trigger it.  There are no other freezable
    workqueues.
    
    Greetings,
    Rafael
    -
    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/
    
    
    \
     
     \ /
      Last update: 2007-03-21 23:39    [from the cache]
    ©2003-2008