On Fri, Apr 20, 2007 at 10:54:36AM +0200, Rafael J. Wysocki wrote: > > Hmm, can't we do something like this instead: > > --- > kernel/kthread.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > Index: linux-2.6.21-rc7/kernel/kthread.c > =================================================================== > --- linux-2.6.21-rc7.orig/kernel/kthread.c > +++ linux-2.6.21-rc7/kernel/kthread.c > @@ -13,6 +13,7 @@ > #include <linux/file.h> > #include <linux/module.h> > #include <linux/mutex.h> > +#include <linux/freezer.h> > #include <asm/semaphore.h> > > /* > @@ -232,6 +233,15 @@ int kthread_stop(struct task_struct *k) > > /* Now set kthread_should_stop() to true, and wake it up. */ > kthread_stop_info.k = k; > + if (!(current->flags & PF_NOFREEZE)) { > + /* If we are freezable, the freezer will wait for us */ > + task_lock(k); > + k->flags |= PF_NOFREEZE; > + if (frozen(k)) > + k->flags &= ~PF_FROZEN; > + > + task_unlock(k); > + }
Yes, we can do this for now since the tasks have only two freeze states, namely Freezeable and Non Freezeable. But with more events like cpu-hotplug and kprobes using the process freezer, the simple check if(!(current->flags & PF_NOFREEZE)) may not suffice and something like if(!(current->flags & PFE_ALL & global_freeze_mask)) /* global_freeze_mask is the mask of the events for which the system is freezing. */ appears to be racy. Not that we cannot work it out ;-) However, I was attempting to solve the generic problem where A waits on B and B is frozen. If A is freezeable (under one of the events) then the freezer will fail. So a solution would be for A to somehow inform B of the dependency and postpone it's freezing. Since akpm mentioned that flush_workqueue() needs to go, I guess, I am ok with fixing only kthread_stop/kthread_should_stop for the moment. Unless I can spot any other valid case :) > wake_up_process(k); > put_task_struct(k); > Thanks and Regards gautham. -- Gautham R Shenoy Linux Technology Center IBM India. "Freedom comes with a price tag of responsibility, which is still a bargain, because Freedom is priceless!" - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/