linux-kernel - [PATCH] sched/membarrier: Fix membarrier-rseq fence command missing from query bitmask

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Message-Id: <20220124165643.17247-1-mathieu.desnoyers@efficios.com>
Date:   Mon, 24 Jan 2022 11:56:43 -0500
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Peter Oskolkov <posk@...gle.com>, stable@...r.kernel.org
Subject: [PATCH] sched/membarrier: Fix membarrier-rseq fence command missing from query bitmask

The membarrier command MEMBARRIER_CMD_QUERY allows querying the
available membarrier commands. When the membarrier-rseq fence commands
were added, a new MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK was
introduced with the intent to expose them with the MEMBARRIER_CMD_QUERY
command, the but it was never added to MEMBARRIER_CMD_BITMASK.

The membarrier-rseq fence commands are therefore not wired up with the
query command.

Rename MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK to
MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK (the bitmask is not a command
per-se), and change the erroneous
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ_BITMASK (which does not
actually exist) to MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ.

Wire up MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK in
MEMBARRIER_CMD_BITMASK. Fixing this allows discovering availability of
the membarrier-rseq fence feature.

Fixes: 2a36ab717e8f ("rseq/membarrier: Add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Peter Oskolkov <posk@...gle.com>
Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: <stable@...r.kernel.org> # 5.10+
---
 kernel/sched/membarrier.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index b5add64d9698..3d2825408e3a 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -147,11 +147,11 @@
 #endif

 #ifdef CONFIG_RSEQ
-#define MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK		\
+#define MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK		\
 	(MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ			\
-	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ_BITMASK)
+	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ)
 #else
-#define MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK	0
+#define MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK	0
 #endif

 #define MEMBARRIER_CMD_BITMASK						\
@@ -159,7 +159,8 @@
 	| MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED			\
 	| MEMBARRIER_CMD_PRIVATE_EXPEDITED				\
 	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED			\
-	| MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK)
+	| MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK		\
+	| MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK)

 static void ipi_mb(void *info)
 {
-- 
2.17.1