On Mon, May 21, 2018 at 01:42:00PM +0800, Xiao Yang wrote:
> 1) According to fcntl(2) manpage, A single process always gets F_UNLCK in
> the l_type field when using fcntl(F_GETLK) to acquire the existing lock
> set by itself because it could convert the existing lock to a new lock
> unconditionally. So we need another process to check if the lock exists.
I used to do that, eventaully I deleted it because we don't need
to check in another process in this case.
Thanks,
Xiong
>
> 2) Remove redundant exit(0).
>
> Signed-off-by: Xiao Yang <yangx.jy@xxxxxxxxxxxxxx>
> ---
> src/t_locks_execve.c | 24 ++++++++++++++++++------
> 1 file changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/src/t_locks_execve.c b/src/t_locks_execve.c
> index 9ad2dc3..d99d7de 100644
> --- a/src/t_locks_execve.c
> +++ b/src/t_locks_execve.c
> @@ -8,6 +8,7 @@
> #include <errno.h>
> #include <pthread.h>
> #include <unistd.h>
> +#include <sys/types.h>
> #include <sys/wait.h>
>
> static void err_exit(char *op, int errn)
> @@ -32,12 +33,24 @@ struct flock fl = {
>
> static void checklock(int fd)
> {
> - if (fcntl(fd, F_GETLK, &fl) < 0)
> - err_exit("getlk", errno);
> - if (fl.l_type == F_UNLCK) {
> - printf("record lock is not preserved across execve(2)\n");
> - exit(1);
> + pid_t pid;
> +
> + pid = fork();
> + if (pid < 0)
> + err_exit("fork", errno);
> +
> + if (!pid) {
> + if (fcntl(fd, F_GETLK, &fl) < 0)
> + err_exit("getlk", errno);
> + if (fl.l_type == F_UNLCK) {
> + printf("record lock is not preserved across execve(2)\n");
> + exit(1);
> + }
> + exit(0);
> }
> +
> + waitpid(pid, NULL, 0);
> +
> exit(0);
> }
>
> @@ -52,7 +65,6 @@ int main(int argc, char **argv)
> if (argc == 3) {
> fd = atoi(argv[2]);
> checklock(fd);
> - exit(0);
> }
>
> fd = open(argv[1], O_WRONLY|O_CREAT, 0755);
> --
> 1.8.3.1
>
>
>
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