| Message ID | 20220319020316.142479-1-libang.linuxer@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | ARC: remove redundant READ_ONCE() in cmpxchg loop | expand |
On 3/18/22 19:03, Bang Li wrote: > This patch reverts commit 7082a29c22ac ("ARC: use ACCESS_ONCE in cmpxchg > loop"). > > It is not necessary to use READ_ONCE() because cmpxchg contains barrier. We > can get it from commit d57f727264f1 ("ARC: add compiler barrier to LLSC > based cmpxchg"). > > Signed-off-by: Bang Li <libang.linuxer@gmail.com> Indeed this is not needed. However have you checked the code with and/wo this change to see if it builds the same. -Vineet > --- > arch/arc/kernel/smp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c > index 78e6d069b1c1..56c23f3e1309 100644 > --- a/arch/arc/kernel/smp.c > +++ b/arch/arc/kernel/smp.c > @@ -274,7 +274,7 @@ static void ipi_send_msg_one(int cpu, enum ipi_msg_type msg) > * and read back old value > */ > do { > - new = old = READ_ONCE(*ipi_data_ptr); > + new = old = *ipi_data_ptr; > new |= 1U << msg; > } while (cmpxchg(ipi_data_ptr, old, new) != old); >
diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c index 78e6d069b1c1..56c23f3e1309 100644 --- a/arch/arc/kernel/smp.c +++ b/arch/arc/kernel/smp.c @@ -274,7 +274,7 @@ static void ipi_send_msg_one(int cpu, enum ipi_msg_type msg) * and read back old value */ do { - new = old = READ_ONCE(*ipi_data_ptr); + new = old = *ipi_data_ptr; new |= 1U << msg; } while (cmpxchg(ipi_data_ptr, old, new) != old);
This patch reverts commit 7082a29c22ac ("ARC: use ACCESS_ONCE in cmpxchg loop"). It is not necessary to use READ_ONCE() because cmpxchg contains barrier. We can get it from commit d57f727264f1 ("ARC: add compiler barrier to LLSC based cmpxchg"). Signed-off-by: Bang Li <libang.linuxer@gmail.com> --- arch/arc/kernel/smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)