On 12/03/2014 05:20 PM, Ola Liljedahl wrote:
Ping!
Needed more review for this.
On 1 December 2014 at 14:34, Ola Liljedahl <[email protected]> wrote:
Signed-off-by: Ola Liljedahl <[email protected]>
---
Replaced an atomic RMW add with separate load, add and store operations.
This avoids generating a "locked" instruction on x86 which implies unnecessary
strong memory ordering and improves performance. This change could also prove
beneficial on other architectures.
platform/linux-generic/odp_ticketlock.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/platform/linux-generic/odp_ticketlock.c
b/platform/linux-generic/odp_ticketlock.c
index 6c5e74e..1e67ff5 100644
--- a/platform/linux-generic/odp_ticketlock.c
+++ b/platform/linux-generic/odp_ticketlock.c
@@ -32,7 +32,10 @@ void odp_ticketlock_lock(odp_ticketlock_t *ticketlock)
void odp_ticketlock_unlock(odp_ticketlock_t *ticketlock)
{
- _odp_atomic_u32_add_mm(&ticketlock->cur_ticket, 1, _ODP_MEMMODEL_RLS);
+ uint32_t cur = _odp_atomic_u32_load_mm(&ticketlock->cur_ticket,
+ _ODP_MEMMODEL_RLX);
+ _odp_atomic_u32_store_mm(&ticketlock->cur_ticket, cur + 1,
+ _ODP_MEMMODEL_RLS);
Isn't this code racy? Some threads can read cur at the same time, then
delay (interrupt or whatever) then do store.
And as result store will have wrong cut_ticket value.
Maxim.
#if defined __OCTEON__
odp_sync_stores(); /* SYNCW to flush write buffer */
--
1.9.1
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