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* miscfuncs.cc (yield): Revert (after researching) to calling SleepEx with 0.

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We don't want to actually sleep when calling this function.
This commit is contained in:
Christopher Faylor 2013-06-08 16:39:52 +00:00
parent 1eaf9215cb
commit 1952976a1b
2 changed files with 16 additions and 15 deletions
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5
winsup/cygwin/ChangeLog
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@ -1,3 +1,8 @@
2013-06-08 Christopher Faylor <me.cygwin2013@cgf.cx>
* miscfuncs.cc (yield): Revert (after researching) to calling SleepEx
with 0. We don't want to actually sleep when calling this function.
2013-06-08 Christopher Faylor <me.cygwin2013@cgf.cx> 2013-06-08 Christopher Faylor <me.cygwin2013@cgf.cx>
* cygwait.cc (cygwait): Remove lock around sig retrieval since this * cygwait.cc (cygwait): Remove lock around sig retrieval since this

16
winsup/cygwin/miscfuncs.cc
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@ -237,25 +237,21 @@ check_iovec (const struct iovec *iov, int iovcnt, bool forwrite)
} }
/* Try hard to schedule another thread. /* Try hard to schedule another thread.
Remember not to call this in a lock condition or you'll potentially
Note: Don't call yield under _cygtls::lock conditions. It results in suffer starvation. */
potential starvation, especially on a single-CPU system, because
_cygtls::lock also calls yield when waiting for the lock. */
void void
yield () yield ()
{ {
int prio = GetThreadPriority (GetCurrentThread ()); int prio = GetThreadPriority (GetCurrentThread ());
SetThreadPriority (GetCurrentThread (), THREAD_PRIORITY_IDLE); SetThreadPriority (GetCurrentThread (), THREAD_PRIORITY_IDLE);
for (int i = 0; i < 2; i++)
{
/* MSDN implies that SleepEx will force scheduling of other threads. /* MSDN implies that SleepEx will force scheduling of other threads.
Unlike SwitchToThread() the documentation does not mention other Unlike SwitchToThread() the documentation does not mention other
cpus so, presumably (hah!), this + using a lower priority will cpus so, presumably (hah!), this + using a lower priority will
stall this thread temporarily and cause another to run. stall this thread temporarily and cause another to run.
Note: Don't use 0 timeout. This takes a lot of CPU if something (stackoverflow and others seem to confirm that setting this thread
goes wrong. */ to a lower priority and calling Sleep with a 0 paramenter will
SleepEx (1L, false); have this desired effect) */
} Sleep (0L);
SetThreadPriority (GetCurrentThread (), prio); SetThreadPriority (GetCurrentThread (), prio);
} }