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    SubjectRe: [PATCH 1/8] Enhance process freezer interface for usage beyond software suspend
    Hi!

    > This patch provides an interface to extend the use of the process
    > freezer beyond Suspend.
    >
    > The tasks can selectively mark themselves to be exempted from specific
    > freeze events like SUSPEND /KPROBES/CPU_HOTPLUG.
    >
    > This patch however, *does not* sort non freezable threads into
    > different categories based on the freeze events. Thus all
    > tasks which were previously marked PF_NOFREEZE are now
    > exempted from freezer using
    > freezer_exempt(FE_ALL);
    > which means exempt from all kinds of freezes.
    >
    > Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
    > Cc: Pavel Machek <pavel@ucw.cz>
    > Cc: Rafael J. Wysocki <rjw@sisk.pl>
    > Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

    Actually no, I was not in cc.

    > +/* Per process freezer specific flags */
    > +#define PF_FE_SUSPEND 0x00008000 /* This thread should not be frozen
    > + * for suspend
    > + */
    > +
    > +#define PF_FE_KPROBES 0x00000010 /* This thread should not be frozen
    > + * for Kprobes
    > + */

    Just put the comment before the define for long comments?


    > -#ifdef CONFIG_PM
    > +#if defined(CONFIG_PM) || defined(CONFIG_HOTPLUG_CPU) || \
    > + defined(CONFIG_KPROBES)

    Should we create CONFIG_FREEZER?

    > Index: linux-2.6.21-rc5/kernel/softlockup.c
    > ===================================================================
    > --- linux-2.6.21-rc5.orig/kernel/softlockup.c
    > +++ linux-2.6.21-rc5/kernel/softlockup.c
    > @@ -96,7 +96,7 @@ static int watchdog(void * __bind_cpu)
    > struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
    >
    > sched_setscheduler(current, SCHED_FIFO, &param);
    > - current->flags |= PF_NOFREEZE;
    > + freezer_exempt(FE_ALL);
    >
    > /*
    > * Run briefly once per second to reset the softlockup timestamp.

    Hmmm, I do not really like softlockup watchdog running during suspend.
    Can we make this freezeable and make watchdog shut itself off while
    suspending?

    > Index: linux-2.6.21-rc5/kernel/rcutorture.c
    > ===================================================================
    > --- linux-2.6.21-rc5.orig/kernel/rcutorture.c
    > +++ linux-2.6.21-rc5/kernel/rcutorture.c
    > @@ -559,7 +559,7 @@ rcu_torture_fakewriter(void *arg)
    >
    > VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task started");
    > set_user_nice(current, 19);
    > - current->flags |= PF_NOFREEZE;
    > + freezer_exempt(FE_ALL);


    Fix rcutorture instead. It has no business running while suspending.

    >
    > do {
    > schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
    > @@ -590,7 +590,7 @@ rcu_torture_reader(void *arg)
    >
    > VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
    > set_user_nice(current, 19);
    > - current->flags |= PF_NOFREEZE;
    > + freezer_exempt(FE_ALL);
    >

    Same here.

    Eventually, we should fix apm, too.

    > Index: linux-2.6.21-rc5/init/do_mounts_initrd.c
    > ===================================================================
    > --- linux-2.6.21-rc5.orig/init/do_mounts_initrd.c
    > +++ linux-2.6.21-rc5/init/do_mounts_initrd.c
    > @@ -55,7 +55,7 @@ static void __init handle_initrd(void)
    > sys_mount(".", "/", NULL, MS_MOVE, NULL);
    > sys_chroot(".");
    >
    > - current->flags |= PF_NOFREEZE;
    > + freezer_exempt(FE_ALL);
    > pid = kernel_thread(do_linuxrc, "/linuxrc", SIGCHLD);
    > if (pid > 0) {
    > while (pid != sys_wait4(-1, NULL, 0, NULL))

    Does this mean we have userland /linuxrc running with PF_NOFREEZE?
    That would be very bad...

    > --- linux-2.6.21-rc5.orig/kernel/kprobes.c
    > +++ linux-2.6.21-rc5/kernel/kprobes.c
    > @@ -104,7 +104,7 @@ static int __kprobes check_safety(void)
    > {
    > int ret = 0;
    > #if defined(CONFIG_PREEMPT) && defined(CONFIG_PM)

    Eh? Why does kprobes code depend on config_pm?

    Pavel

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