Re: blocking file lock functions (lockf,flock,fcntl) do not return after timer signal

["linux-os \(Dick Johnson\)" <linux-os@analogic.com>]

On Wed, 12 Oct 2005, Alex Riesen wrote:

> On 10/12/05, "Dieter Müller (BOI GmbH)" <dieter.mueller@boi.at> wrote:
>> bug description:
>>
>> flock, lockf, fcntl do not return even after the signal SIGALRM  has
>> been raised and the signal handler function has been executed
>> the functions should return with a return value EWOULDBLOCK as described
>> in the man pages
>
> To confirm:
>
> #include <unistd.h>
> #include <sys/time.h>
> #include <sys/file.h>
> #include <time.h>
> #include <signal.h>
>
> void alrm(int sig)
> {
>    write(2, "timeout\n", 8);
> }
>
> int main(int argc, char* argv[])
> {
>    struct itimerval tv = {
>        .it_interval = {.tv_sec = 10, .tv_usec = 0},
>        .it_value = {.tv_sec = 10, .tv_usec = 0},
>    };
>    struct itimerval otv;
>
>    signal(SIGALRM, alrm);
>    setitimer(ITIMER_REAL, &tv, &otv);
>    int fd = open(argv[1], O_RDWR);
>    if ( fd < 0 )
>    {
>        perror(argv[1]);
>        return 1;
>    }
>    printf("locking...\n");
>    if ( flock(fd, LOCK_EX) < 0 )
>    {
>        perror("flock");
>        return 1;
>    }
>    printf("sleeping...\n");
>    int ch;
>    read(0, &ch, 1);
>    close(fd);
>    return 0;
> }
> -

Does your 'signal()' impliment POSIX or BSD signals? You don't know.
It's whatever the 'C' runtime library got built for. You need to
use sigaction() so you can set the flags to give you your intended
action.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.48 BogoMips).
Warning : 98.36% of all statistics are fiction.

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