Mercurial > hg > nginx
view src/core/ngx_crc.h @ 6080:4296627f385a stable-1.6
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().
author | Roman Arutyunyan <arut@nginx.com> |
---|---|
date | Wed, 04 Feb 2015 16:22:43 +0300 |
parents | d620f497c50f |
children |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #ifndef _NGX_CRC_H_INCLUDED_ #define _NGX_CRC_H_INCLUDED_ #include <ngx_config.h> #include <ngx_core.h> /* 32-bit crc16 */ static ngx_inline uint32_t ngx_crc(u_char *data, size_t len) { uint32_t sum; for (sum = 0; len; len--) { /* * gcc 2.95.2 x86 and icc 7.1.006 compile * that operator into the single "rol" opcode, * msvc 6.0sp2 compiles it into four opcodes. */ sum = sum >> 1 | sum << 31; sum += *data++; } return sum; } #endif /* _NGX_CRC_H_INCLUDED_ */