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    SubjectRe: [Suspend-devel] [BUG] 3.7-rc regression bisected: s2disk fails to resume image: Processes could not be frozen, cannot continue resuming
    Hi!

    > > And from suspend_ioctls.h:
    > > #define SNAPSHOT_IOC_MAGIC '3'
    > > #define SNAPSHOT_FREEZE _IO(SNAPSHOT_IOC_MAGIC, 1)
    > >
    > > My mistake, should be '3' instead of 3.
    >
    > OK... The thing to test, then, is what does __usermodehelper_disable()
    > return to freeze_processes(). If that's where this -EAGAIN comes from,
    > we at least have a plausible theory re what's going on.
    >
    > freeze_processes() uses __usermodehelper_disable() to stop any new userland
    > processes spawned by UMH (modprobe, etc.) and waits for ones it might be
    > waiting for to complete. Then it does try_to_freeze_tasks(), which
    > freezes remaining userland, carefully skipping the current thread.
    > However, it misses the possibility that current thread might have been
    > spawned by something that had been launched by UMH, with UMH waiting
    > for it. Which is the case of everything spawned by linuxrc.
    >
    > I'd try something like diff below, but I'm *NOT* familiar with swsusp at
    > all; it's not for mainline until ACKed by swsusp folks.
    >
    > diff --git a/kernel/kmod.c b/kernel/kmod.c
    > index fb32636..d968882 100644
    > --- a/kernel/kmod.c
    > +++ b/kernel/kmod.c
    > @@ -571,7 +571,8 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
    > DECLARE_COMPLETION_ONSTACK(done);
    > int retval = 0;
    >
    > - helper_lock();
    > + if (!(current->flags & PF_FREEZER_SKIP))
    > + helper_lock();
    > if (!khelper_wq || usermodehelper_disabled) {
    > retval = -EBUSY;
    > goto out;
    > @@ -611,7 +612,8 @@ wait_done:
    > out:
    > call_usermodehelper_freeinfo(sub_info);
    > unlock:
    > - helper_unlock();
    > + if (!(current->flags & PF_FREEZER_SKIP))
    > + helper_unlock();
    > return retval;
    > }
    > EXPORT_SYMBOL(call_usermodehelper_exec);

    PF_FREEZER_SKIP flag is manipulated at about 1000 places, so I'm not
    sure this will nest correctly. They seem to be in form of

    |= FREEZER_SKIP
    schedule()
    &= ~FREEZER_SKIP

    so this should be safe, but...

    Pavel
    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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