Messages in this thread | | | Date | Thu, 2 Oct 2014 14:15:53 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 00/11] nested sleeps, fixes and debug infrastructure |
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On Thu, Oct 02, 2014 at 12:22:51PM +0200, Peter Zijlstra wrote: > Subject: audit,wait: Fixup kauditd_thread wait loop > > The kauditd_thread wait loop is a bit iffy; it has a number of problems: > > - calls try_to_freeze() before schedule(); you typically want the > thread to re-evaluate the sleep condition when unfreezing, also > freeze_task() issues a wakeup. > > - it unconditionally does the {add,remove}_wait_queue(), even when the > sleep condition is false. > > Introduce a new wait_event() variant, wait_event_freezable() that does > all the right things and employ it here. > > Cc: Oleg Nesterov <oleg@redhat.com> > Cc: Eric Paris <eparis@redhat.com> > Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > include/linux/wait.h | 25 +++++++++++++++++++++++++ > kernel/audit.c | 11 +---------- > 2 files changed, 26 insertions(+), 10 deletions(-) > > --- a/include/linux/wait.h > +++ b/include/linux/wait.h > @@ -266,6 +266,31 @@ do { \ > __wait_event(wq, condition); \ > } while (0) > > +#define __wait_event_freezable(wq, condition) \ > + (void)___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0, \ > + schedule(); try_to_freeze()) > + > +/** > + * wait_event - sleep until a condition gets true or freeze (for kthreads) > + * @wq: the waitqueue to wait on > + * @condition: a C expression for the event to wait for > + * > + * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute > + * to system load) until the @condition evaluates to true. The > + * @condition is checked each time the waitqueue @wq is woken up. > + * > + * wake_up() has to be called after changing any variable that could > + * change the result of the wait condition. > + */ > +#define wait_event_freezable(wq, condition) \ > +do { \ > + WARN_ON_ONCE(!(current->flags & PF_KTHREAD)); \ > + might_sleep(); \ > + if (condition) \ > + break; \ > + __wait_event_freezable(wq, condition); \ > +} while (0) > + > #define __wait_event_timeout(wq, condition, timeout) \ > ___wait_event(wq, ___wait_cond_timeout(condition), \ > TASK_UNINTERRUPTIBLE, 0, timeout, \
Bah, that doesn't compile, because there already appears to be one, hidden in freezer.h. Now I can't actually tell if it does the same thing or not.
Rafael?
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