| Message ID | ZfQUxnNTO9AJmzwc@libra05 (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [net,v2] rds: introduce acquire/release ordering in acquire/release_in_xmit() | expand |
On Fri, Mar 15, 2024 at 06:28:38PM +0900, Yewon Choi wrote: > acquire/release_in_xmit() work as bit lock in rds_send_xmit(), so they > are expected to ensure acquire/release memory ordering semantics. > However, test_and_set_bit/clear_bit() don't imply such semantics, on > top of this, following smp_mb__after_atomic() does not guarantee release > ordering (memory barrier actually should be placed before clear_bit()). > > Instead, we use clear_bit_unlock/test_and_set_bit_lock() here. > > Fixes: 0f4b1c7e89e6 ("rds: fix rds_send_xmit() serialization") > Fixes: 1f9ecd7eacfd ("RDS: Pass rds_conn_path to rds_send_xmit()") > Signed-off-by: Yewon Choi <woni9911@gmail.com> > --- > Changes in v1 -> v2: > - Added missing Fixes tags > > net/rds/send.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/net/rds/send.c b/net/rds/send.c > index 5e57a1581dc6..8f38009721b7 100644 > --- a/net/rds/send.c > +++ b/net/rds/send.c > @@ -103,13 +103,12 @@ EXPORT_SYMBOL_GPL(rds_send_path_reset); > > static int acquire_in_xmit(struct rds_conn_path *cp) > { > - return test_and_set_bit(RDS_IN_XMIT, &cp->cp_flags) == 0; > + return test_and_set_bit_lock(RDS_IN_XMIT, &cp->cp_flags) == 0; > } > > static void release_in_xmit(struct rds_conn_path *cp) > { > - clear_bit(RDS_IN_XMIT, &cp->cp_flags); > - smp_mb__after_atomic(); > + clear_bit_unlock(RDS_IN_XMIT, &cp->cp_flags); > /* > * We don't use wait_on_bit()/wake_up_bit() because our waking is in a > * hot path and finding waiters is very rare. We don't want to walk > -- > 2.43.0 > LGTM Thanks, Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Hello: This patch was applied to netdev/net.git (main) by Paolo Abeni <pabeni@redhat.com>: On Fri, 15 Mar 2024 18:28:38 +0900 you wrote: > acquire/release_in_xmit() work as bit lock in rds_send_xmit(), so they > are expected to ensure acquire/release memory ordering semantics. > However, test_and_set_bit/clear_bit() don't imply such semantics, on > top of this, following smp_mb__after_atomic() does not guarantee release > ordering (memory barrier actually should be placed before clear_bit()). > > Instead, we use clear_bit_unlock/test_and_set_bit_lock() here. > > [...] Here is the summary with links: - [net,v2] rds: introduce acquire/release ordering in acquire/release_in_xmit() https://git.kernel.org/netdev/net/c/1422f28826d2 You are awesome, thank you!
diff --git a/net/rds/send.c b/net/rds/send.c index 5e57a1581dc6..8f38009721b7 100644 --- a/net/rds/send.c +++ b/net/rds/send.c @@ -103,13 +103,12 @@ EXPORT_SYMBOL_GPL(rds_send_path_reset); static int acquire_in_xmit(struct rds_conn_path *cp) { - return test_and_set_bit(RDS_IN_XMIT, &cp->cp_flags) == 0; + return test_and_set_bit_lock(RDS_IN_XMIT, &cp->cp_flags) == 0; } static void release_in_xmit(struct rds_conn_path *cp) { - clear_bit(RDS_IN_XMIT, &cp->cp_flags); - smp_mb__after_atomic(); + clear_bit_unlock(RDS_IN_XMIT, &cp->cp_flags); /* * We don't use wait_on_bit()/wake_up_bit() because our waking is in a * hot path and finding waiters is very rare. We don't want to walk
acquire/release_in_xmit() work as bit lock in rds_send_xmit(), so they are expected to ensure acquire/release memory ordering semantics. However, test_and_set_bit/clear_bit() don't imply such semantics, on top of this, following smp_mb__after_atomic() does not guarantee release ordering (memory barrier actually should be placed before clear_bit()). Instead, we use clear_bit_unlock/test_and_set_bit_lock() here. Fixes: 0f4b1c7e89e6 ("rds: fix rds_send_xmit() serialization") Fixes: 1f9ecd7eacfd ("RDS: Pass rds_conn_path to rds_send_xmit()") Signed-off-by: Yewon Choi <woni9911@gmail.com> --- Changes in v1 -> v2: - Added missing Fixes tags net/rds/send.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)