On 12/19/13 12:45, Davidlohr Bueso wrote: > From: Thomas Gleixner <[email protected]> > > That's essential, if you want to hack on futexes. > > Cc: Ingo Molnar <[email protected]> > Cc: Darren Hart <[email protected]> > Acked-by: Peter Zijlstra <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Paul E. McKenney <[email protected]> > Cc: Mike Galbraith <[email protected]> > Cc: Jeff Mahoney <[email protected]> > Cc: Linus Torvalds <[email protected]> > Cc: Scott Norton <[email protected]> > Cc: Tom Vaden <[email protected]> > Cc: Aswin Chandramouleeswaran <[email protected]> > Cc: Waiman Long <[email protected]> > Cc: Jason Low <[email protected]> > Signed-off-by: Thomas Gleixner <[email protected]> > Signed-off-by: Davidlohr Bueso <[email protected]> > --- > kernel/futex.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 57 insertions(+) > > diff --git a/kernel/futex.c b/kernel/futex.c > index 577481d..af1fc31 100644 > --- a/kernel/futex.c > +++ b/kernel/futex.c > @@ -69,6 +69,63 @@ > > #include "locking/rtmutex_common.h" > > +/* > + * Basic futex operation and ordering guarantees: > + * > + * The waiter reads the futex value in user space and calls > + * futex_wait(). It computes the hash bucket and acquires the hash
does It refer to "the waiter" or to futex_wait()? I read it as referring to the waiter, but ISTM that the comments are using It to refer to futex_wait()... ??? Thanks. > + * bucket lock. After that it reads the futex user space value again > + * and verifies that the data has not changed. If it has not changed > + * it enqueues itself into the hash bucket, releases the hash > + * bucket lock and schedules. > + * > + * The waker side modifies the user space value of the futex and calls > + * futex_wake(). It computes the hash bucket and acquires the hash > + * bucket lock. Then it looks for waiters on that futex in the hash > + * bucket and wakes them. > + * > + * Note that the spin_lock serializes waiters and wakers, so that the > + * following scenario is avoided: > + * -- ~Randy -- 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/
