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release_in_xmit() clears RDS_IN_XMIT with clear_bit_unlock() and then checks waitqueue_active() to decide whether anyone needs waking. clear_bit_unlock() is only a release operation: it orders the critical section before the bit clear, but does not order the subsequent plain load of the wait queue head after it. The waiter side does the mirror image - it adds itself to the wait queue and then tests the bit. That is the classic store-buffering pattern: the releasing CPU can read the wait queue as empty while the waiting CPU still reads the bit as set, so the sleeper is never woken. The waiters are rds_conn_shutdown() and rds_tcp_reset_callbacks(), both in uninterruptible wait_event() with no timeout. A lost wake-up strands the shutdown worker on its single-threaded workqueue until some other sender releases the bit again - and on a connection that is being torn down precisely because it failed, there may never be another sender. The barrier used to be there: release_in_xmit() did clear_bit() followed by smp_mb__after_atomic() until commit1422f28826("rds: introduce acquire/release ordering in acquire/release_in_xmit()") folded both into clear_bit_unlock(), which strengthened the lock hand-off but silently dropped the full barrier the wake-up check depends on. The refill counterpart, release_refill() in net/rds/ib_recv.c, still carries its smp_mb__after_atomic() for exactly this reason. Use wq_has_sleeper(), which is waitqueue_active() preceded by the required full barrier. Fixes:1422f28826("rds: introduce acquire/release ordering in acquire/release_in_xmit()") Signed-off-by: Allison Henderson <achender@kernel.org> Link: https://patch.msgid.link/20260828223921.202913-2-achender@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>