Mounting it did not change the behaviour on the affected systems. The affected system claims to support POSIX semaphores: _POSIX_SEMAPHORES is true and sysconf(_SC_SEMAPHORES) confirms this.Įdit 1: I've added more detail on the software versions in use and removed some irrelevant comments.Įdit 2: /dev/shm is mounted on the good systems and not mounted on the bad systems. The sem_open() userspace is in librt which we link against dynamically and librt is present on the affected systems. #define ENOSYS 38 /* Function not implemented */ Man sem_open suggests this errno means sem_open() is not supported by system. (and also works on CentOS 5 kernel 2.6.18 /lib/librt-2.5.so /lib/i686/nosegneg/libpthread-2.5.so). Systems with issue are Slackware 10.1.0 kernel 2.6.11 /lib/librt-2.3.4.so /lib/libpthread-0.10.so, but the same code works on the much older RedHat 9 kernel 2.4.20 /lib/librt-2.3.2.so /lib/tls/libpthread-0.29.so. Sample code to reproduce below (the code works fine on CentOS / RedHat).Īre there any kernel or system configuration options that could cause this? Other suggestions? I have two Slackware Linux systems on which the POSIX semaphore sem_open() call fails with errno set to 38.

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