Commit 26cff4e2 authored Oct 08, 2012 by Hildner, Christian Committed by Thomas Gleixner Oct 09, 2012

timers: Fix endless looping between cascade() and internal_add_timer()



Adding two (or more) timers with large values for "expires" (they have
to reside within tv5 in the same list) leads to endless looping
between cascade() and internal_add_timer() in case CONFIG_BASE_SMALL
is one and jiffies are crossing the value 1 << 18. The bug was
introduced between 2.6.11 and 2.6.12 (and survived for quite some
time).

This patch ensures that when cascade() is called timers within tv5 are
not added endlessly to their own list again, instead they are added to
the next lower tv level tv4 (as expected).

Signed-off-by: Christian Hildner <christian.hildner@siemens.com>
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Link: http://lkml.kernel.org/r/98673C87CB31274881CFFE0B65ECC87B0F5FC1963E@DEFTHW99EA4MSX.ww902.siemens.net


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org

parent db8c2469

kernel/timer.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -63,6 +63,7 @@ EXPORT_SYMBOL(jiffies_64);
		#define TVR_SIZE (1 << TVR_BITS)
		#define TVN_MASK (TVN_SIZE - 1)
		#define TVR_MASK (TVR_SIZE - 1)
		#define MAX_TVAL ((unsigned long)((1ULL << (TVR_BITS + 4*TVN_BITS)) - 1))

		struct tvec {
		struct list_head vec[TVN_SIZE];
		@@ -359,11 +360,12 @@ __internal_add_timer(struct tvec_base base, struct timer_list timer)
		vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK);
		} else {
		int i;
		/* If the timeout is larger than 0xffffffff on 64-bit
		* architectures then we use the maximum timeout:
		/* If the timeout is larger than MAX_TVAL (on 64-bit
		* architectures or with CONFIG_BASE_SMALL=1) then we
		* use the maximum timeout.
		*/
		if (idx > 0xffffffffUL) {
		idx = 0xffffffffUL;
		if (idx > MAX_TVAL) {
		idx = MAX_TVAL;
		expires = idx + base->timer_jiffies;
		}
		i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;

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