Messages in this thread | | | Date | Thu, 1 Nov 2012 23:55:31 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 2/3] alarmtimer: Using the alarmtimer_get_rtcdev for all posix clock interface |
| |
On Thu, 1 Nov 2012, Chuansheng Liu wrote: > > Some posix clock interface directly use the variable rtcdev, > cleanup it here by alarmtimer_get_rtcdev(). > > Signed-off-by: liu chuansheng <chuansheng.liu@intel.com> > --- > kernel/time/alarmtimer.c | 13 ++++++------- > 1 files changed, 6 insertions(+), 7 deletions(-) > > diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c > index 4fc17cb..5490fa8 100644 > --- a/kernel/time/alarmtimer.c > +++ b/kernel/time/alarmtimer.c > @@ -86,11 +86,10 @@ static int alarmtimer_rtc_add_device(struct device *dev, > return -1; > > mutex_lock(&rtcdev_mutex); > - if (!rtcdev) { > - rtcdev = rtc; > - /* hold a reference so it doesn't go away */ > - get_device(dev); > - } > + rtcdev = rtc; > + /* hold a reference so it doesn't go away */ > + get_device(dev); > +
Brilliant.
rtcdev = NULL
CPU0 CPU 1
alarmtimer_rtc_add_device(A) if (rtcdev) alarmtimer_rtc_add_device(B) return -EBUSY; if (rtcdev) mutex_lock(); return -EBUSY; rtcdev = A; mutex_lock(); mutex_unlock;
bla = alarmtimer_rtc_get_device()
So bla = A mutex_lock() returns rtcdev = B; mutex_unlock();
The next call to alarmtimer_rtc_get_device() will return B. Not what you want. Maybe you want that, but then your patch is missing an explanation why you want that and why this would be a desired behaviour.
Thanks,
tglx
| |