On 09/11, Cedric Le Goater wrote: > > Eric W. Biederman wrote: > > Cedric Le Goater <clg at fr.ibm.com> writes: > > > >> message queues can signal a process waiting for a message. > >> > >> this patch replaces the pid_t value with a struct pid to avoid pid wrap > >> around problems. > >> > >> Signed-off-by: Cedric Le Goater <clg at fr.ibm.com> > >> Cc: Eric Biederman <ebiederm at xmission.com> > >> Cc: Andrew Morton <akpm at osdl.org> > >> Cc: containers at lists.osdl.org > > > > Signed-off-by: Eric Biederman <ebiederm at xmission.com> > > > > I was just about to send out this patch in a couple more hours. > > Well, you did the same with the usb/devio.c and friends :) > > > So expect the fact we wrote the same code is a good sign :) > > How does oleg feel about it ? I've seen some long thread on possible race > conditions with put_pid() and solutions with rcu. I didn't quite get all of > it ... it will need another run for me. I assume you are talking about this patch: http://marc.theaimsgroup.com/?l=linux-mm-commits&m=115773820415171 I think it's ok, info->notify_owner is always used under info->lock. This is simple. If, for example, mqueue_read_file() didn't take info->lock, then we have a problem: pid_nr() may read a freed memory in case when __do_notify()->put_pid() happens at the same time. In this context info->notify_owner is a usual refcounted object, no special attention is needed. Oleg.
