linux-kernel - [RFC PATCH 2/5] selftests/rseq: Remove volatile from __rseq

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Date:   Mon, 17 Jan 2022 15:39:22 -0500
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        "H . Peter Anvin" <hpa@...or.com>, Paul Turner <pjt@...gle.com>,
        linux-api@...r.kernel.org,
        Christian Brauner <christian.brauner@...ntu.com>,
        Florian Weimer <fw@...eb.enyo.de>, David.Laight@...LAB.COM,
        carlos@...hat.com,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [RFC PATCH 2/5] selftests/rseq: Remove volatile from __rseq_abi

This is done in preparation for the selftest uplift to become compatible
with glibc-2.35.

All accesses to the __rseq_abi fields are volatile, but remove the
volatile from the TLS variable declaration, otherwise we are stuck with
volatile for the upcoming rseq_get_abi() helper.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
---
 tools/testing/selftests/rseq/rseq.c | 4 ++--
 tools/testing/selftests/rseq/rseq.h | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
index 7159eb777fd3..a0d8eed24035 100644
--- a/tools/testing/selftests/rseq/rseq.c
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -31,7 +31,7 @@
 
 #define ARRAY_SIZE(arr)	(sizeof(arr) / sizeof((arr)[0]))
 
-__thread volatile struct rseq __rseq_abi = {
+__thread struct rseq __rseq_abi = {
 	.cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
 };
 
@@ -93,7 +93,7 @@ int rseq_register_current_thread(void)
 		goto end;
 	}
 	if (errno != EBUSY)
-		__rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
+		RSEQ_WRITE_ONCE(__rseq_abi.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
 	ret = -1;
 	__rseq_refcount--;
 end:
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index 3f63eb362b92..f971a9217145 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -43,7 +43,7 @@
 #define RSEQ_INJECT_FAILED
 #endif
 
-extern __thread volatile struct rseq __rseq_abi;
+extern __thread struct rseq __rseq_abi;
 extern int __rseq_handled;
 
 #define rseq_likely(x)		__builtin_expect(!!(x), 1)
@@ -140,9 +140,9 @@ static inline uint32_t rseq_current_cpu(void)
 static inline void rseq_clear_rseq_cs(void)
 {
 #ifdef __LP64__
-	__rseq_abi.rseq_cs.ptr = 0;
+	RSEQ_WRITE_ONCE(__rseq_abi.rseq_cs.ptr, 0);
 #else
-	__rseq_abi.rseq_cs.ptr.ptr32 = 0;
+	RSEQ_WRITE_ONCE(__rseq_abi.rseq_cs.ptr.ptr32, 0);
 #endif
 }
 
-- 
2.17.1