On Thu, 2012-07-05 at 20:51 -0700, Christian Kujau wrote:
> On Mon, 2 Jul 2012 at 14:04, Li Zhong wrote:
> > This patch tries to fix a dead loop in async_synchronize_full(), which
> > could be seen when preemption is disabled on a single cpu machine.
>
> This helps in my case[0], will this patch be included in -rc6?
>
> Thanks,
> Christian.
>
> [0] https://lists.ozlabs.org/pipermail/linuxppc-dev/2012-July/098922.html
>
Seems it was not included in -rc6 :( I'll try to resend it today
Thanks,
Zhong
>
> > void async_synchronize_full(void)
> > {
> > do {
> > async_synchronize_cookie(next_cookie);
> > } while (!list_empty(&async_running) || !
> > list_empty(&async_pending));
> > }
> >
> > async_synchronize_cookie() calls async_synchronize_cookie_domain() with
> > &async_running as the default domain to synchronize.
> >
> > However, there might be some works in the async_pending list from other
> > domains. On a single cpu system, without preemption, there is no chance
> > for the other works to finish, so async_synchronize_full() enters a dead
> > loop.
> >
> > It seems async_synchronize_full() wants to synchronize all entries in
> > all running lists(domains), so maybe we could just check the entry_count
> > to know whether all works are finished.
> >
> > Currently, async_synchronize_cookie_domain() expects a non-NULL running
> > list ( if NULL, there would be NULL pointer dereference ), so maybe a
> > NULL pointer could be used as an indication for the functions to
> > synchronize all works in all domains.
> >
> > Reported-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> > Signed-off-by: Li Zhong <zh...@linux.vnet.ibm.com>
> > Tested-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> > ---
> > kernel/async.c | 13 +++++++++----
> > 1 file changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/async.c b/kernel/async.c
> > index bd0c168..32d8dc9 100644
> > --- a/kernel/async.c
> > +++ b/kernel/async.c
> > @@ -86,6 +86,13 @@ static async_cookie_t __lowest_in_progress(struct
> > list_head *running)
> > {
> > struct async_entry *entry;
> >
> > + if (!running) { /* just check the entry count */
> > + if (atomic_read(&entry_count))
> > + return 0; /* smaller than any cookie */
> > + else
> > + return next_cookie;
> > + }
> > +
> > if (!list_empty(running)) {
> > entry = list_first_entry(running,
> > struct async_entry, list);
> > @@ -236,9 +243,7 @@ EXPORT_SYMBOL_GPL(async_schedule_domain);
> > */
> > void async_synchronize_full(void)
> > {
> > - do {
> > - async_synchronize_cookie(next_cookie);
> > - } while (!list_empty(&async_running) || !list_empty(&async_pending));
> > + async_synchronize_cookie_domain(next_cookie, NULL);
> > }
> > EXPORT_SYMBOL_GPL(async_synchronize_full);
> >
> > @@ -258,7 +263,7 @@ EXPORT_SYMBOL_GPL(async_synchronize_full_domain);
> > /**
> > * async_synchronize_cookie_domain - synchronize asynchronous function
> > calls within a certain domain with cookie checkpointing
> > * @cookie: async_cookie_t to use as checkpoint
> > - * @running: running list to synchronize on
> > + * @running: running list to synchronize on, NULL indicates all lists
> > *
> > * This function waits until all asynchronous function calls for the
> > * synchronization domain specified by the running list @list submitted
> > --
> > 1.7.9.5
> >
> > --
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