[PATCH] hrtimer: round up relative start time on low-res arches

CONFIG_TIME_LOW_RES is a temporary way for architectures to signal that
they simply return xtime in do_gettimeoffset().  In this corner-case we
want to round up by resolution when starting a relative timer, to avoid
short timeouts.  This will go away with the GTOD framework.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

7 files changed, 37 insertions, 1 deletions

diff --git a/arch/frv/Kconfig b/arch/frv/Kconfig
index 60a617aff8ba..e08383712370 100644
--- a/arch/frv/Kconfig
+++ b/arch/frv/Kconfig
@@ -25,6 +25,10 @@ config GENERIC_HARDIRQS
         bool
         default n
 
+config TIME_LOW_RES
+        bool
+        default y
+
 mainmenu "Fujitsu FR-V Kernel Configuration"
 
 source "init/Kconfig"
diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig
index 80940d712acf..98308b018a35 100644
--- a/arch/h8300/Kconfig
+++ b/arch/h8300/Kconfig
@@ -33,6 +33,10 @@ config GENERIC_CALIBRATE_DELAY
         bool
         default y
 
+config TIME_LOW_RES
+        bool
+        default y
+
 config ISA
         bool
         default y
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 96b919828053..8849439e88dd 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -21,6 +21,10 @@ config GENERIC_CALIBRATE_DELAY
         bool
         default y
 
+config TIME_LOW_RES
+        bool
+        default y
+
 config ARCH_MAY_HAVE_PC_FDC
         bool
         depends on Q40 || (BROKEN && SUN3X)
diff --git a/arch/m68knommu/Kconfig b/arch/m68knommu/Kconfig
index e2a6e8648960..e50858dbc237 100644
--- a/arch/m68knommu/Kconfig
+++ b/arch/m68knommu/Kconfig
@@ -29,6 +29,10 @@ config GENERIC_CALIBRATE_DELAY
         bool
         default y
 
+config TIME_LOW_RES
+        bool
+        default y
+
 source "init/Kconfig"
 
 menu "Processor type and features"
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 7c914a4c67c3..eca33cfa8a4c 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -29,6 +29,11 @@ config GENERIC_CALIBRATE_DELAY
         bool
         default y
 
+config TIME_LOW_RES
+        bool
+        depends on SMP
+        default y
+
 config GENERIC_ISA_DMA
         bool
 
diff --git a/arch/v850/Kconfig b/arch/v850/Kconfig
index 04494638b963..e7fc3e500342 100644
--- a/arch/v850/Kconfig
+++ b/arch/v850/Kconfig
@@ -28,6 +28,10 @@ config GENERIC_IRQ_PROBE
         bool
         default y
 
+config TIME_LOW_RES
+        bool
+        default y
+
 # Turn off some random 386 crap that can affect device config
 config ISA
         bool
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 2b6e1757aedd..5ae51f1bc7c8 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -418,8 +418,19 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
         /* Switch the timer base, if necessary: */
         new_base = switch_hrtimer_base(timer, base);
 
-        if (mode == HRTIMER_REL)
+        if (mode == HRTIMER_REL) {
                 tim = ktime_add(tim, new_base->get_time());
+                /*
+                 * CONFIG_TIME_LOW_RES is a temporary way for architectures
+                 * to signal that they simply return xtime in
+                 * do_gettimeoffset(). In this case we want to round up by
+                 * resolution when starting a relative timer, to avoid short
+                 * timeouts. This will go away with the GTOD framework.
+                 */
+#ifdef CONFIG_TIME_LOW_RES
+                tim = ktime_add(tim, base->resolution);
+#endif
+        }
         timer->expires = tim;
 
         enqueue_hrtimer(timer, new_base);