Messages in this thread | | | Subject | Re: [Bug #11989] Suspend failure on NForce4-based boards due to chanes in stop_machine | From | Peter Zijlstra <> | Date | Tue, 11 Nov 2008 14:49:01 +0100 |
| |
On Tue, 2008-11-11 at 14:36 +0100, Vegard Nossum wrote: > On Tue, Nov 11, 2008 at 11:52 AM, Ingo Molnar <mingo@elte.hu> wrote: > > [ Cc:-ed workqueue/locking/suspend-race-condition experts. ] > > Heh. I am not expert, but I looked at the code. The obvious suspicious > thing to see is the use of unpaired barriers? Maybe like this: > > 47 static void set_state(enum stopmachine_state newstate) > 48 { > 49 /* Reset ack counter. */ > 50 atomic_set(&thread_ack, num_threads); > 51 smp_wmb(); > > + /* force ordering between thread_ack/state */ > > 52 state = newstate; > 53 } > 54 > 55 /* Last one to ack a state moves to the next state. */ > 56 static void ack_state(void) > 57 { > 58 if (atomic_dec_and_test(&thread_ack)) > > Maybe > + /* force ordering between thread_ack/state */ > + smp_rmb(); > here?
all atomic ops that have return values imply a full barrier, iirc
> 59 set_state(state + 1); > 60 } > 61 > > Or maybe I am wrong. But Documentation/memory-barriers.txt is rather > explicit on this point. > > > Vegard >
| |