[PATCH v2 05/37] hrtimer: Ensure POSIX compliance (relative CLOCK_REALTIME hrtimers)

Anna-Maria Gleixner
2017-10-22T21:43:09Z

[-- Attachment #1: hrtimer--Fix-Posix-compliance--relative-CLOCK_REALTIME-hrtimers-.patch --]
[-- Type: text/plain, Size: 1298 bytes --]

POSIX specification defines, that relative CLOCK_REALTIME timers are not
affected by clock modifications. Those timers have to use CLOCK_MONOTONIC
to ensure POSIX compliance.

The introduction of the additional mode HRTIMER_MODE_PINNED broke this
requirement for pinned timers. There is no user space visible impact
because user space timers are not using the pinned mode, but for
consistency reasons this needs to be fixed.

Check whether the mode has the HRTIMER_MODE_REL bit set instead of
comparing with HRTIMER_MODE_ABS.

Fixes: 597d0275736d ("timers: Framework for identifying pinned timers")

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
kernel/time/hrtimer.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1104,7 +1104,12 @@ static void __hrtimer_init(struct hrtime

cpu_base = raw_cpu_ptr(&hrtimer_bases);

- if (clock_id == CLOCK_REALTIME && mode != HRTIMER_MODE_ABS)
+ /*
+ * Posix magic: Relative CLOCK_REALTIME timers are not affected by
+ * clock modifications, so they needs to become CLOCK_MONOTONIC to
+ * ensure Posix compliance.
+ */
+ if (clock_id == CLOCK_REALTIME && mode & HRTIMER_MODE_REL)
clock_id = CLOCK_MONOTONIC;

base = hrtimer_clockid_to_base(clock_id);