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pthread_cond_timedwait: fix timeout calculation

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Due to rounding in the timeout calculation it may happen that the timeout
stored in ms becomes 0, but actually some time (us or ns) are left to wait.
With threads on various priorities (vbox) this may end up in endless loops.

Fixes #2311
This commit is contained in:
Alexander Boettcher 2017-03-08 11:41:24 +01:00 committed by Christian Helmuth
parent 7a4f4f1adc
commit 261edf59a9
1 changed files with 40 additions and 7 deletions
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47
repos/libports/src/lib/pthread/thread.cc
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@ -586,9 +586,44 @@ extern "C" {
}
static unsigned long timespec_to_ms(const struct timespec ts)
static uint64_t timeout_ms(struct timespec currtime,
struct timespec abstimeout)
{
return (ts.tv_sec * 1000) + (ts.tv_nsec / (1000 * 1000));
enum { S_IN_MS = 1000, S_IN_NS = 1000 * 1000 * 1000 };
if (currtime.tv_nsec >= S_IN_NS) {
currtime.tv_sec += currtime.tv_nsec / S_IN_NS;
currtime.tv_nsec = currtime.tv_nsec % S_IN_NS;
}
if (abstimeout.tv_nsec >= S_IN_NS) {
abstimeout.tv_sec += abstimeout.tv_nsec / S_IN_NS;
abstimeout.tv_nsec = abstimeout.tv_nsec % S_IN_NS;
}
/* check whether absolute timeout is in the past */
if (currtime.tv_sec > abstimeout.tv_sec)
return 0;
uint64_t diff_ms = (abstimeout.tv_sec - currtime.tv_sec) * S_IN_MS;
uint64_t diff_ns = 0;
if (abstimeout.tv_nsec >= currtime.tv_nsec)
diff_ns = abstimeout.tv_nsec - currtime.tv_nsec;
else {
/* check whether absolute timeout is in the past */
if (diff_ms == 0)
return 0;
diff_ns = S_IN_NS - currtime.tv_nsec + abstimeout.tv_nsec;
diff_ms -= S_IN_MS;
}
diff_ms += diff_ns / 1000 / 1000;
/* if there is any diff then let the timeout be at least 1 MS */
if (diff_ms == 0 && diff_ns != 0)
return 1;
return diff_ms;
}
@ -597,7 +632,6 @@ extern "C" {
const struct timespec *__restrict abstime)
{
int result = 0;
Alarm::Time timeout = 0;
if (!cond || !*cond)
return EINVAL;
@ -615,10 +649,9 @@ extern "C" {
else {
struct timespec currtime;
clock_gettime(CLOCK_REALTIME, &currtime);
unsigned long abstime_ms = timespec_to_ms(*abstime);
unsigned long currtime_ms = timespec_to_ms(currtime);
if (abstime_ms > currtime_ms)
timeout = abstime_ms - currtime_ms;
Alarm::Time timeout = timeout_ms(currtime, *abstime);
try {
c->signal_sem.down(timeout);
} catch (Timeout_exception) {