Core: fixed a race resulting in extra sem_post()'s. The mtx->wait counter was not decremented if we were able to obtain the lock right after incrementing it. This resulted in unneeded sem_post() calls, eventually leading to EOVERFLOW errors being logged, "sem_post() failed while wake shmtx (75: Value too large for defined data type)". To close the race, mtx->wait is now decremented if we obtain the lock right after incrementing it in ngx_shmtx_lock(). The result can become -1 if a concurrent ngx_shmtx_unlock() decrements mtx->wait before the added code does. However, that only leads to one extra iteration in the next call of ngx_shmtx_lock().

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


ngx_include="unistd.h";      . auto/include
ngx_include="inttypes.h";    . auto/include
ngx_include="limits.h";      . auto/include
ngx_include="sys/filio.h";   . auto/include
ngx_include="sys/param.h";   . auto/include
ngx_include="sys/mount.h";   . auto/include
ngx_include="sys/statvfs.h"; . auto/include
ngx_include="crypt.h";       . auto/include