linux-kernel - [PATCH] jiffies: Revert mistaken conversion of NSEC_PER_SEC to TICK

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Message-Id: <1488880534-3777-1-git-send-email-fweisbec@gmail.com>
Date:   Tue,  7 Mar 2017 10:55:34 +0100
From:   Frederic Weisbecker <fweisbec@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Meelis Roos <mroos@...ux.ee>
Subject: [PATCH] jiffies: Revert mistaken conversion of NSEC_PER_SEC to TICK_NSEC

The following commit:

	93825f2ec736f30e034ab7c9d56b42849c5b00da
	("jiffies: Reuse TICK_NSEC instead of NSEC_PER_JIFFY")

has introduced a wrong rename due to a confusion between NSEC_PER_JIFFY
and NSEC_PER_SEC. As a result, the calculation of refined jiffies got
broken, triggering lockups.

Reported-and-tested-by: Meelis Roos <mroos@...ux.ee>
Cc: Meelis Roos <mroos@...ux.ee>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 kernel/time/jiffies.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index 7906b3f..4977191 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -125,7 +125,7 @@ int register_refined_jiffies(long cycles_per_second)
 	shift_hz += cycles_per_tick/2;
 	do_div(shift_hz, cycles_per_tick);
 	/* Calculate nsec_per_tick using shift_hz */
-	nsec_per_tick = (u64)TICK_NSEC << 8;
+	nsec_per_tick = (u64)NSEC_PER_SEC << 8;
 	nsec_per_tick += (u32)shift_hz/2;
 	do_div(nsec_per_tick, (u32)shift_hz);
 
-- 
2.7.4