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authorJ. Bruce Fields <bfields@citi.umich.edu>2010-07-20 15:23:15 -0700
committerThomas Gleixner <tglx@linutronix.de>2010-07-23 15:08:12 +0200
commit866e26115cba6b59cec669b6307599e3e4440491 (patch)
treed6a4920f298608e23c8fc56f8902ae5773be8fc4 /kernel/timer.c
parentb37fa16e78d6f9790462b3181602a26b5af36260 (diff)
timers: Document meaning of deferrable timer
Steal some text from 6e453a67510 "Add support for deferrable timers". A reader shouldn't have to dig through the git logs for the basic description of a deferrable timer. Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu> Cc: johnstul@us.ibm.com Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/timer.c')
-rw-r--r--kernel/timer.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/timer.c b/kernel/timer.c
index ee305c8d4e1..ce98685cd1c 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -90,8 +90,13 @@ static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;
/*
* Note that all tvec_bases are 2 byte aligned and lower bit of
- * base in timer_list is guaranteed to be zero. Use the LSB for
- * the new flag to indicate whether the timer is deferrable
+ * base in timer_list is guaranteed to be zero. Use the LSB to
+ * indicate whether the timer is deferrable.
+ *
+ * A deferrable timer will work normally when the system is busy, but
+ * will not cause a CPU to come out of idle just to service it; instead,
+ * the timer will be serviced when the CPU eventually wakes up with a
+ * subsequent non-deferrable timer.
*/
#define TBASE_DEFERRABLE_FLAG (0x1)