Messages in this thread | | | Date | Tue, 11 Nov 2008 14:36:19 +0100 | From | "Vegard Nossum" <> | Subject | Re: [Bug #11989] Suspend failure on NForce4-based boards due to chanes in stop_machine |
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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?
59 set_state(state + 1); 60 } 61
Or maybe I am wrong. But Documentation/memory-barriers.txt is rather explicit on this point.
Vegard
-- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036
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