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author | Meador Inge <meadori@codesourcery.com> | 2014-06-13 14:02:04 +0530 |
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committer | Siddhesh Poyarekar <siddhesh@redhat.com> | 2014-06-13 14:02:04 +0530 |
commit | 995a46bbfba9964e328e3947130919d8bd3cd62a (patch) | |
tree | c36f1da1cc528a8cfc1d891310be2599c0507532 /ChangeLog.7 | |
parent | febf6cc58c36cd5a978b8b5faedb5a932eb44c98 (diff) | |
download | glibc-995a46bbfba9964e328e3947130919d8bd3cd62a.tar.gz glibc-995a46bbfba9964e328e3947130919d8bd3cd62a.tar.xz glibc-995a46bbfba9964e328e3947130919d8bd3cd62a.zip |
get_nprocs: Only return explictly set cache values (BZ #16996)
The implementation of __get_nprocs uses a stactic variable to cache the value of the current number of processors. The caching breaks when 'time (NULL) == 0': $ cat nproc.c #include <stdio.h> #include <time.h> #include <sys/time.h> int main(int argc, char *argv[]) { time_t t; struct timeval tv = {0, 0}; printf("settimeofday({0, 0}, NULL) = %d\n", settimeofday(&tv, NULL)); t = time(NULL); printf("Time: %d, CPUs: %d\n", (unsigned int)t, get_nprocs()); return 0; } $ gcc -O3 nproc.c $ ./a.out settimeofday({0, 0}, NULL) = -1 Time: 1401311578, CPUs: 4 $ sudo ./a.out settimeofday({0, 0}, NULL) = 0 Time: 0, CPUs: 0 The problem is with the condition used to check whether a cached value should be returned or not: static int cached_result; static time_t timestamp; time_t now = time (NULL); time_t prev = timestamp; atomic_read_barrier (); if (now == prev) return cached_result; This patch fixes the problem by ensuring that 'cached_result' has been set at least once before returning it.
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