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SubjectRe: EINTR vs ERESTARTSYS, ERESTARTSYS not defined
On Thu, Nov 22, 2001 at 04:15:40PM +0100, Andreas Schwab wrote:

| Phil Howard <phil-linux-kernel@ipal.net> writes:
|
| |> The accept() call does indeed return errno==ERESTARTSYS to user space
| |> when coming back from signal handling, even though other things like
| |> poll() return errno==EINTR. This would not really be a problem except
| |> for this in include/linux/errno.h starting at line 6:
| |>
| |> +=============================================================================
| |> | #ifdef __KERNEL__
| |> |
| |> | /* Should never be seen by user programs */
| |> | #define ERESTARTSYS 512
| |> | #define ERESTARTNOINTR 513
| |> | #define ERESTARTNOHAND 514 /* restart if no handler.. */
| |> | #define ENOIOCTLCMD 515 /* No ioctl command */
| |> +=============================================================================
| |>
| |> So which way is it _supposed_ to be (so someone can patch things up
| |> to make it consistent):
| |>
| |> 1. User space should never see ERESTARTSYS from any system call
|
| Yes. The kernel either transforms it to EINTR, or restarts the syscall
| when the signal handler returns.

This code periodically quits because sometimes there is an unknown errno.

for (;;) {
memset( arg_sock_addr, 0, * arg_sock_addrlen );
new_fd = accept( arg_sockfd_list[fd_index], arg_sock_addr, arg_sock_addrlen );
if ( new_fd >= 0 ) break;
if ( errno == EINTR ) continue;
if ( errno == ECONNABORTED ) continue;
break;
}
if ( new_fd <= 2 ) {
perror( "daemon_accept: accept" );
if ( fd_count > 1 ) continue;
_exit( 1 ); // not very graceful
}

Then strace showed ERESTARTSYS happening, and when I changed the code to:

for (;;) {
memset( arg_sock_addr, 0, * arg_sock_addrlen );
new_fd = accept( arg_sockfd_list[fd_index], arg_sock_addr, arg_sock_addrlen );
if ( new_fd >= 0 ) break;
if ( errno == EINTR ) continue;
if ( errno == ERESTARTSYS ) continue;
if ( errno == ECONNABORTED ) continue;
break;
}
if ( new_fd <= 2 ) {
perror( "daemon_accept: accept" );
if ( fd_count > 1 ) continue;
_exit( 1 ); // not very graceful
}

it started working solidly. I had to define __KERNEL__ to get it. But I don't
want to leave that in there for portable code.

Could this be an unintended leak of ERESTARTSYS? I take it that what the comments
say is what is intended, and that what I actually get isn't.

--
-----------------------------------------------------------------
| Phil Howard - KA9WGN | Dallas | http://linuxhomepage.com/ |
| phil-nospam@ipal.net | Texas, USA | http://phil.ipal.org/ |
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