On 12/19/13 12:45, Davidlohr Bueso wrote: > From: Thomas Gleixner <t...@linutronix.de> > > That's essential, if you want to hack on futexes. > > Cc: Ingo Molnar <mi...@kernel.org> > Cc: Darren Hart <dvh...@linux.intel.com> > Acked-by: Peter Zijlstra <pet...@infradead.org> > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> > Cc: Mike Galbraith <efa...@gmx.de> > Cc: Jeff Mahoney <je...@suse.com> > Cc: Linus Torvalds <torva...@linux-foundation.org> > Cc: Scott Norton <scott.nor...@hp.com> > Cc: Tom Vaden <tom.va...@hp.com> > Cc: Aswin Chandramouleeswaran <as...@hp.com> > Cc: Waiman Long <waiman.l...@hp.com> > Cc: Jason Low <jason.l...@hp.com> > Signed-off-by: Thomas Gleixner <t...@linutronix.de> > Signed-off-by: Davidlohr Bueso <davidl...@hp.com> > --- > 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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
