linux-kernel - [PATCH v2 04/20] provide xtime_update() which does not require the caller to hold xtime

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Date:	Thu, 27 Jan 2011 15:59:10 +0100
From:	Torben Hohn <torbenh@....de>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>, johnstul@...ibm.com,
	Thomas Gleixner <tglx@...utronix.de>, yong.zhang0@...il.com,
	hch@...radead.org
Subject: [PATCH v2 04/20] provide xtime_update() which does not require the
	caller to hold xtime_lock

like do_timer().
this change avoids having this code sequence all over the place:

seq_writelock( &xtime_lock );
do_timer();
seq_writeunlock( &xtime_lock );

Signed-off-by: Torben Hohn <torbenh@....de>
---
 include/linux/sched.h     |    1 +
 kernel/time/timekeeping.c |   13 +++++++++++++
 2 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 738ec15..c0b0bb7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2045,6 +2045,7 @@ extern void release_uids(struct user_namespace *ns);
 #include <asm/current.h>
 
 extern void do_timer(unsigned long ticks);
+extern void xtime_update(unsigned long ticks);
 
 extern int wake_up_state(struct task_struct *tsk, unsigned int state);
 extern int wake_up_process(struct task_struct *tsk);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 6085fa5..8dd6e38 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -978,3 +978,16 @@ void get_xtime_and_monotonic_offset(struct timespec *xts, struct timespec *tom)
 			*tom = wall_to_monotonic;
 	} while (read_seqretry(&xtime_lock, seq));
 }
+
+/**
+ * xtime_update() - advances the timekeeping infrastructure
+ * @ticks:	number of ticks, that have elapsed since the last call.
+ *
+ * this function needs to be called with interrupts disabled.
+ */
+void xtime_update(unsigned long ticks)
+{
+	write_seqlock(&xtime_lock);
+	do_timer(ticks);
+	write_sequnlock(&xtime_lock);
+}

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