Messages in this thread Patch in this message | | | Date | Fri, 3 Aug 2012 13:07:45 +0800 | From | majianpeng <> | Subject | [PATCH] block: Don't use static to define "void *p" in show_partition_start(). |
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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 <majianpeng@gmail.com> --- block/genhd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/genhd.c b/block/genhd.c index cac7366..d839723 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) -- 1.7.9.5 | |