linux-kernel - [PATCH 4.2.y-ckt 15/64] posix-timers: Handle relative timers with CONFIG_TIME_LOW

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Message-Id: <1454625887-18915-16-git-send-email-kamal@canonical.com>
Date:	Thu,  4 Feb 2016 14:43:58 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Helge Deller <deller@....de>,
	John Stultz <john.stultz@...aro.org>,
	linux-m68k@...ts.linux-m68k.org, dhowells@...hat.com,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 15/64] posix-timers: Handle relative timers with CONFIG_TIME_LOW_RES proper

4.2.8-ckt4 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Thomas Gleixner <tglx@...utronix.de>

commit 572c39172684c3711e4a03c9a7380067e2b0661c upstream.

As Helge reported for timerfd we have the same issue in posix timers. We
return remaining time larger than the programmed relative time to user space
in case of CONFIG_TIME_LOW_RES=y. Use the proper function to adjust the extra
time added in hrtimer_start_range_ns().

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Helge Deller <deller@....de>
Cc: John Stultz <john.stultz@...aro.org>
Cc: linux-m68k@...ts.linux-m68k.org
Cc: dhowells@...hat.com
Link: http://lkml.kernel.org/r/20160114164159.450510905@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 kernel/time/posix-timers.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 31d11ac..f2826c3 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -760,7 +760,7 @@ common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
 	    (timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE))
 		timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv);
 
-	remaining = ktime_sub(hrtimer_get_expires(timer), now);
+	remaining = __hrtimer_expires_remaining_adjusted(timer, now);
 	/* Return 0 only, when the timer is expired and not pending */
 	if (remaining.tv64 <= 0) {
 		/*
-- 
1.9.1