linux-kernel - [RFC PATCH 04/15] selftests/rseq: Remove volatile from __rseq

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Date:   Mon, 24 Jan 2022 12:12:42 -0500
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        "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, Shuah Khan <shuah@...nel.org>,
        linux-kselftest@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [RFC PATCH 04/15] 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 | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
index bfe1b2692ffc..1f905b60728a 100644
--- a/tools/testing/selftests/rseq/rseq.c
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -30,7 +30,7 @@
 #include "../kselftest.h"
 #include "rseq.h"
 
-__thread volatile struct rseq_abi __rseq_abi = {
+__thread struct rseq_abi __rseq_abi = {
 	.cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED,
 };
 
@@ -92,7 +92,7 @@ int rseq_register_current_thread(void)
 		goto end;
 	}
 	if (errno != EBUSY)
-		__rseq_abi.cpu_id = RSEQ_ABI_CPU_ID_REGISTRATION_FAILED;
+		RSEQ_WRITE_ONCE(__rseq_abi.cpu_id, RSEQ_ABI_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 cb6bbc53b586..d580f8e9c001 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_abi __rseq_abi;
+extern __thread struct rseq_abi __rseq_abi;
 extern int __rseq_handled;
 
 #define rseq_likely(x)		__builtin_expect(!!(x), 1)
@@ -139,7 +139,7 @@ static inline uint32_t rseq_current_cpu(void)
 
 static inline void rseq_clear_rseq_cs(void)
 {
-	__rseq_abi.rseq_cs.arch.ptr = 0;
+	RSEQ_WRITE_ONCE(__rseq_abi.rseq_cs.arch.ptr, 0);
 }
 
 /*
-- 
2.17.1