On Fri, 22 Feb 2019 at 17:01, Glyn Gowing <> wrote: > I have a program (attached) that works correctly on my mac but does > not work with Cygwin on Windows 10. I'm running the latest version of
> What happens in the buggy execution is that the child obtains a lock > before the parent releases it. I'm using mmap and a pthread_mutex_t > object along with fork(). Again, this exact code works correctly on my > Mac running Mojave. On further analysis, the call to > pthread_mutexattr_setpshared(attr, PTHREAD_PROCESS_SHARED); is failing. The error is EINVAL (22) Invalid argument. This suggests that pthread mutexes cannot be shared between processes by using shared memory in cygwin. I have not attempted to determine if this is working as expected, or if this is a bug, or a limitation in the Windows environment. I have attached my files: smtest2.c - my heavily modified version of OP's original. smtest2.txt - output from running this version.showing error. smtest3.c - my version which uses 2 pthreads in a single process smtest3.txt - output from running this version, showing OP's expected results. HTH Doug
gcc -std=c11 -pthread -Wall -Wextra -Werror -o smtest2 smtest2.c && ./smtest2 22 Invalid argument pthread_mutexattr_setpshared: No error make: *** [Makefile:30: smtest2] Error 1
smtest3.c
Description: Binary data
gcc -std=c11 -pthread -Wall -Wextra -Werror -o smtest3 smtest3.c && ./smtest3 1550925866 - both : attr, lock, lock->next: 0x600000430 0x600000410 0x600000470 1550925866 - Child : checking lock (0x600000470) - Before sleeping 5 seconds. 1550925866 - Parent: acquiring lock (0x600000470) 1550925866 - Parent: acquired lock (0x600000470) - Before sleeping 10 seconds. 1550925871 - Child : acquiring lock (0x600000470) - After sleeping 5 seconds. 1550925876 - Parent: unlocking lock (0x600000470) - After sleeping 10 seconds. 1550925876 - Parent: unlocked lock (0x600000470) - Before sleeping 5 seconds to let child catch up. 1550925876 - Child : acquired lock (0x600000470) - Before sleeping 3 seconds. 1550925879 - Child : unlocking lock (0x600000470) - After sleeping 3 seconds. 1550925879 - Child : unlocked lock (0x600000470). 1550925881 - - After sleeping 5 seconds to let child catch up.
smtest2.c
Description: Binary data
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