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 <[email protected]>
---
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
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 <[email protected]>
> ---
> 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 <[email protected]>
Hello:
This patch was applied to netdev/net.git (main)
by Paolo Abeni <[email protected]>:
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!
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