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Commit f781fb51 authored by Yewon Choi's avatar Yewon Choi Committed by Sasha Levin
Browse files

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: 0f4b1c7e ("rds: fix rds_send_xmit() serialization")
Fixes: 1f9ecd7e ("RDS: Pass rds_conn_path to rds_send_xmit()")
Signed-off-by: default avatarYewon Choi <woni9911@gmail.com>
Reviewed-by: default avatarMichal Kubiak <michal.kubiak@intel.com>
Link: https://lore.kernel.org/r/ZfQUxnNTO9AJmzwc@libra05


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 84c51041

net/rds/send.c

+2 −3
Original line number Diff line number Diff line
@@ -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