Author :
cheloha
Date :
2020-08-09 19:15:47
Hash :3c86a58e Message :hardclock(9): fix race with setitimer(2) for ITIMER_VIRTUAL, ITIMER_PROF
The ITIMER_VIRTUAL and ITIMER_PROF per-process interval timers are
updated from hardclock(9). If a timer for the parent process is
enabled the hardclock(9) thread calls itimerdecr() to update and
reload it as needed.
However, in itimerdecr(), after entering itimer_mtx, the thread needs
to double-check that the timer in question is still enabled. While
the hardclock(9) thread is entering itimer_mtx a thread in
setitimer(2) can take the mutex and disable the timer.
If the timer is disabled, itimerdecr() should return 1 to indicate
that the timer has not expired and that no action needs to be taken.
ok kettenis@
cheloha