How can WaitOne hang when used with a timeout?

Ed Sutton

Can any one please offer any theories on how ManualResetEven t.WaitOne
can hang when used with a timeout?

When I notice my USB/Serial devices are no longer receiving
communications, I hit break all, and one of the threads is hanging at:

bool replyReceived =
readerCommand.S ignalReply.Wait One(readerCmd.r xTimeOutMs, false);

Apparently the 1000ms rxTimeOutMs is not working. I have two threads
that wait on this event. This problem has been plaguing me for a long
time. I can not understand how the timeout does not work. If it is a
threading issue, I can not see what it is.

Thanks in advance for any theories or suggestions.

-Ed

May 31 '06 #1

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10409

andrew queisser

"Ed Sutton" <de************ ******@hotmail. com> wrote in message
news:eY******** ******@TK2MSFTN GP02.phx.gbl...

Can any one please offer any theories on how ManualResetEven t.WaitOne can
hang when used with a timeout?

When I notice my USB/Serial devices are no longer receiving
communications, I hit break all, and one of the threads is hanging at:

bool replyReceived =
readerCommand.S ignalReply.Wait One(readerCmd.r xTimeOutMs, false);

Apparently the 1000ms rxTimeOutMs is not working. I have two threads that
wait on this event. This problem has been plaguing me for a long time. I
can not understand how the timeout does not work. If it is a threading
issue, I can not see what it is.

Thanks in advance for any theories or suggestions.

Other than checking whether rxTimeOutMs contains a sane value when you enter
the WaitOne my only suggestion would be to try passing 'true' for the second
parameter.

Andrew

May 31 '06 #2

Ed Sutton

andrew queisser wrote:

readerCommand.S ignalReply.Wait One(readerCmd.r xTimeOutMs, false);
Other than checking whether rxTimeOutMs contains a sane value when you enter
the WaitOne my only suggestion would be to try passing 'true' for the second
parameter.

Thank you for your reply.

Yes, rxTimeOutMs is set to 1000 milliseconds.

I do not understand why setting the exitContext parameter to true would
make the timeout work as I expect. I expect it to wait until the
ManualResetEven t is signaled or the timeout occurs. The problem is the
timeout elapses yet it is never signaled.

Any additional thoughts are much appreciated.

-Ed

May 31 '06 #3

andrew queisser

"Ed Sutton" <de************ ******@hotmail. com> wrote in message
news:OQ******** ******@TK2MSFTN GP03.phx.gbl...

andrew queisser wrote:
readerCommand.S ignalReply.Wait One(readerCmd.r xTimeOutMs, false);

Other than checking whether rxTimeOutMs contains a sane value when you
enter the WaitOne my only suggestion would be to try passing 'true' for
the second parameter.

Thank you for your reply.

Yes, rxTimeOutMs is set to 1000 milliseconds.

I do not understand why setting the exitContext parameter to true would
make the timeout work as I expect. I expect it to wait until the
ManualResetEven t is signaled or the timeout occurs. The problem is the
timeout elapses yet it is never signaled.

Any additional thoughts are much appreciated.

Hi Ed,

Don't really know either, I was just looking at the two parameters to the
function. If you do have a good value for rxTimeoutMs, the only other knob
to play with is the context parameter so I just wanted to make sure you did
try changing that value.

I never fully understood what the exitContext parameter does although I
often use WaitOne. After reading your post I decided it was time to
understand what exitContext means and now I have at least some understanding
of its function. I'm not sure if it really is possible to lead to a deadlock
but perhaps there's another thread running in the same context that the
WaitOne thread was running in. That could lead to a situation where WaitOne
wakes up due to timeout but cannot run because it cannot get into the
context. However, I would expect a deadlock to be more likely when you set
the exitContext to true.

Andrew

Jun 1 '06 #4

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