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From: "tip-bot2 for Frederic Weisbecker" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Frederic Weisbecker <frederic@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	stable@vger.kernel.org, x86 <x86@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: [tip: timers/urgent] timer: Fix wheel index calculation on last level
Date: Fri, 17 Jul 2020 19:49:30 -0000	[thread overview]
Message-ID: <159501537091.4006.13327108405728570679.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20200717140551.29076-2-frederic@kernel.org>

The following commit has been merged into the timers/urgent branch of tip:

Commit-ID:     e2a71bdea81690b6ef11f4368261ec6f5b6891aa
Gitweb:        https://git.kernel.org/tip/e2a71bdea81690b6ef11f4368261ec6f5b6891aa
Author:        Frederic Weisbecker <frederic@kernel.org>
AuthorDate:    Fri, 17 Jul 2020 16:05:40 +02:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Fri, 17 Jul 2020 21:44:05 +02:00

timer: Fix wheel index calculation on last level

When an expiration delta falls into the last level of the wheel, that delta
has be compared against the maximum possible delay and reduced to fit in if
necessary.

However instead of comparing the delta against the maximum, the code
compares the actual expiry against the maximum. Then instead of fixing the
delta to fit in, it sets the maximum delta as the expiry value.

This can result in various undesired outcomes, the worst possible one
being a timer expiring 15 days ahead to fire immediately.

Fixes: 500462a9de65 ("timers: Switch to a non-cascading wheel")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200717140551.29076-2-frederic@kernel.org

---
 kernel/time/timer.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 9a838d3..df1ff80 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -521,8 +521,8 @@ static int calc_wheel_index(unsigned long expires, unsigned long clk)
 		 * Force expire obscene large timeouts to expire at the
 		 * capacity limit of the wheel.
 		 */
-		if (expires >= WHEEL_TIMEOUT_CUTOFF)
-			expires = WHEEL_TIMEOUT_MAX;
+		if (delta >= WHEEL_TIMEOUT_CUTOFF)
+			expires = clk + WHEEL_TIMEOUT_MAX;
 
 		idx = calc_index(expires, LVL_DEPTH - 1);
 	}

  reply	other threads:[~2020-07-17 19:49 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-17 14:05 [PATCH 00/11] timer: Reduce timers softirq v3 Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 01/12] timer: Fix wheel index calculation on last level Frederic Weisbecker
2020-07-17 19:49   ` tip-bot2 for Frederic Weisbecker [this message]
2020-07-17 14:05 ` [PATCH 02/12] timer: Preserve higher bits of expiration on index calculation Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 03/12] timers: Use only bucket expiry for base->next_expiry value Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] " tip-bot2 for Anna-Maria Behnsen
2020-07-17 14:05 ` [PATCH 04/12] timer: Move trigger_dyntick_cpu() to enqueue_timer() Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 05/12] timer: Add comments about calc_index() ceiling work Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 06/12] timer: Optimize _next_timer_interrupt() level iteration Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 07/12] timers: Always keep track of next expiry Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 08/12] timer: Reuse next expiry cache after nohz exit Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 09/12] timer: Expand clk forward logic beyond nohz Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 10/12] timer: Spare timer softirq until next expiry Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 11/12] timer: Remove must_forward_clk Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker
2020-07-17 14:05 ` [PATCH 12/12] timer: Lower base clock forwarding threshold Frederic Weisbecker
2020-07-17 20:00   ` [tip: timers/core] timers: " tip-bot2 for Frederic Weisbecker

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