Patch "rds: introduce acquire/release ordering in acquire/release_in_xmit()" has been added to the 5.4-stable tree

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This is a note to let you know that I've just added the patch titled

    rds: introduce acquire/release ordering in acquire/release_in_xmit()

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     rds-introduce-acquire-release-ordering-in-acquire-re.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit fbbf4862b91a30cf91e7d5a5f1bd1304065be054
Author: Yewon Choi <woni9911@xxxxxxxxx>
Date:   Fri Mar 15 18:28:38 2024 +0900

    rds: introduce acquire/release ordering in acquire/release_in_xmit()
    
    [ Upstream commit 1422f28826d2a0c11e5240b3e951c9e214d8656e ]
    
    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@xxxxxxxxx>
    Reviewed-by: Michal Kubiak <michal.kubiak@xxxxxxxxx>
    Link: https://lore.kernel.org/r/ZfQUxnNTO9AJmzwc@libra05
    Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/rds/send.c b/net/rds/send.c
index 6c2c5667e3a39..c0cebf4b4fe56 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




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