linux-kernel - [tip:x86/timers] x86/tsc: Move sync cleanup to a safe place

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Message-ID: <tip-4c5e3c63752162262c42424147f319b8571a20af@git.kernel.org>
Date:   Tue, 29 Nov 2016 10:30:31 -0800
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     yinghai@...nel.org, bp@...en8.de, linux-kernel@...r.kernel.org,
        mingo@...nel.org, tglx@...utronix.de, hpa@...or.com,
        peterz@...radead.org
Subject: [tip:x86/timers] x86/tsc: Move sync cleanup to a safe place

Commit-ID:  4c5e3c63752162262c42424147f319b8571a20af
Gitweb:     http://git.kernel.org/tip/4c5e3c63752162262c42424147f319b8571a20af
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Sat, 19 Nov 2016 13:47:40 +0000
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 29 Nov 2016 19:23:18 +0100

x86/tsc: Move sync cleanup to a safe place

Cleaning up the stop marker on the control CPU is wrong when we want to add
retry support. Move the cleanup to the starting CPU.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Yinghai Lu <yinghai@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Link: http://lkml.kernel.org/r/20161119134017.892095627@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 arch/x86/kernel/tsc_sync.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index fdb3b7b..8f394eeb 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -267,11 +267,6 @@ void check_tsc_sync_source(int cpu)
 	}
 
 	/*
-	 * Reset it - in case this is a second bootup:
-	 */
-	atomic_set(&stop_count, 0);
-
-	/*
 	 * Wait for the target to start or to skip the test:
 	 */
 	while (atomic_read(&start_count) != cpus - 1) {
@@ -360,6 +355,11 @@ void check_tsc_sync_target(void)
 	 */
 	while (atomic_read(&stop_count) != cpus)
 		cpu_relax();
+
+	/*
+	 * Reset it for the next sync test:
+	 */
+	atomic_set(&stop_count, 0);
 }
 
 #endif /* CONFIG_SMP */