From 0676806707281e27b13d44323bed580a8160b7a4 Mon Sep 17 00:00:00 2001 From: Jianpeng Ma Date: Fri, 3 Aug 2012 10:42:00 +0200 Subject: block: Don't use static to define "void *p" in show_partition_start() I met a odd prblem:read /proc/partitions may return zero. I wrote a file test.c: int main() { char buff[4096]; int ret; int fd; printf("pid=%d\n",getpid()); while (1) { fd = open("/proc/partitions", O_RDONLY); if (fd < 0) { printf("open error %s\n", strerror(errno)); return 0; } ret = read(fd, buff, 4096); if (ret <= 0) printf("ret=%d, %s, %ld\n", ret, strerror(errno), lseek(fd,0,SEEK_CUR)); close(fd); } exit(0); } You can reproduce by: 1:while true;do cat /proc/partitions > /dev/null ;done 2:./test I reviewed the code and found: >> static void *show_partition_start(struct seq_file *seqf, loff_t *pos) >> { >> static void *p; >> >> p = disk_seqf_start(seqf, pos); >> if (!IS_ERR_OR_NULL(p) && !*pos) >> seq_puts(seqf, "major minor #blocks name\n\n"); >> return p; >> } test cat /proc/partitions p = disk_seqf_start()(Not NULL) p = disk_seqf_start()(NULL because pos) if (!IS_ERR_OR_NULL(p) && !*pos) Signed-off-by: Jianpeng Ma Signed-off-by: Jens Axboe --- block/genhd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/genhd.c b/block/genhd.c index cac7366957c..d839723303c 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -835,7 +835,7 @@ static void disk_seqf_stop(struct seq_file *seqf, void *v) static void *show_partition_start(struct seq_file *seqf, loff_t *pos) { - static void *p; + void *p; p = disk_seqf_start(seqf, pos); if (!IS_ERR_OR_NULL(p) && !*pos) -- cgit v1.2.3