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yield: Don't lower thread priority, it leads to starvation

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...and it's not required anymore to have the same effect as the original
code post-XP.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2017-03-08 17:44:15 +01:00
parent 994a4b7dcc
commit 51a993c266
1 changed files with 6 additions and 5 deletions
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11
winsup/cygwin/miscfuncs.cc
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@ -85,17 +85,18 @@ check_iovec (const struct iovec *iov, int iovcnt, bool forwrite)
void void
yield () yield ()
{ {
int prio = GetThreadPriority (GetCurrentThread ()); /* MSDN implies that Sleep will force scheduling of other threads.
SetThreadPriority (GetCurrentThread (), THREAD_PRIORITY_IDLE);
/* 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.
(stackoverflow and others seem to confirm that setting this thread (stackoverflow and others seem to confirm that setting this thread
to a lower priority and calling Sleep with a 0 paramenter will to a lower priority and calling Sleep with a 0 paramenter will
have this desired effect) */ have this desired effect)
CV 2017-03-08: Drop lowering the priority. It leads to potential
starvation and it should not be necessary anymore
since Server 2003. See the MSDN Sleep man page. */
Sleep (0L); Sleep (0L);
SetThreadPriority (GetCurrentThread (), prio);
} }
/* Get a default value for the nice factor. When changing these values, /* Get a default value for the nice factor. When changing these values,