diff options
Diffstat (limited to 'cpukit/score/src/kern_tc.c')
| -rw-r--r-- | cpukit/score/src/kern_tc.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/cpukit/score/src/kern_tc.c b/cpukit/score/src/kern_tc.c index 81c2131008..fa53fcd085 100644 --- a/cpukit/score/src/kern_tc.c +++ b/cpukit/score/src/kern_tc.c @@ -1418,6 +1418,15 @@ static bool sleeping_on_old_rtc(struct thread *td) { + /* + * td_rtcgen is modified by curthread when it is running, + * and by other threads in this function. By finding the thread + * on a sleepqueue and holding the lock on the sleepqueue + * chain, we guarantee that the thread is not running and that + * modifying td_rtcgen is safe. Setting td_rtcgen to zero informs + * the thread that it was woken due to a real-time clock adjustment. + * (The declaration of td_rtcgen refers to this comment.) + */ if (td->td_rtcgen != 0 && td->td_rtcgen != rtc_generation) { td->td_rtcgen = 0; return (true); @@ -1461,6 +1470,7 @@ _Timecounter_Set_clock(const struct bintime *_bt, #ifndef __rtems__ tc_windup(&bt); mtx_unlock_spin(&tc_setclock_mtx); + /* Avoid rtc_generation == 0, since td_rtcgen == 0 is special. */ atomic_add_rel_int(&rtc_generation, 2); sleepq_chains_remove_matching(sleeping_on_old_rtc); |