Re^11: Threads sharing global variable

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Re^12: Threads sharing global variable by BrowserUk (Patriarch) on Mar 06, 2016 at 15:08 UTC
The unlock-and-block part of cond_wait() is atomic; hence, by the time another thread acquires the lock, this first thread is guaranteed to be in a waiting state. But if the signalling thread signals before the other thread(s) reach the wait(); that signal can be lost. lost signals. signals getting lost Lost wakeups in pthreads Lost signals - slow conditions a) spurious wakeups. b) lost signals; c) broadcast deadlock d) unfairness In our approach we use Petri nets to represent the key elements of interactions among threads to identify potential problems such as race conditions, lost signals, and deadlocks. A tool called C2Petri has been developed which converts C-Pthreads programs to the equivalent Petri net model. This tool helps verification of Pthread-based programs. Hundreds more... With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :) In the absence of evidence, opinion is indistinguishable from prejudice.	[reply]
Re^13: Threads sharing global variable by Anonymous Monk on Mar 06, 2016 at 15:25 UTC
Depending on which thread wins the first lock, the first cond_signal() may be redundant. That is: If `set_positive()` won, it proceeds without waiting, and sends the unnecessary signal. This signal is dropped. But the `set_zero()` thread can then also proceed without `cond_wait()`, and subsequently sets the ping-pong going with its own `cond_signal()`.	[reply] [d/l] [select]
Re^14: Threads sharing global variable by BrowserUk (Patriarch) on Mar 06, 2016 at 15:34 UTC
It hangs on Windows; and will eventually hang everywhere if you add any useful code to the while loops. As a coding pattern, ikegami's code is broken by design. End of. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :) In the absence of evidence, opinion is indistinguishable from prejudice.	[reply]
Re^15: Threads sharing global variable by Anonymous Monk on Mar 06, 2016 at 15:45 UTC
Re^16: Threads sharing global variable by BrowserUk (Patriarch) on Mar 06, 2016 at 16:04 UTC
Re^13: Threads sharing global variable by Anonymous Monk on Mar 06, 2016 at 15:31 UTC
Uh. Re: the links you have added. I'm not sure if I follow. The code you posted, is similarly at the mercy of the underlying signaling mechanism.	[reply]
Re^14: Threads sharing global variable by BrowserUk (Patriarch) on Mar 06, 2016 at 15:37 UTC
The code you posted, is similarly at the mercy of the underlying signaling mechanism. My code doesn't hang in its posted form anywhere. And add long running code into the processing loops of any or all of the threads and all threads will always be able to make forward progress. My code works! As posted, and during evolution to realistic scenarios. By design! With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :) In the absence of evidence, opinion is indistinguishable from prejudice.	[reply]