On Sun, 29 Jul 2007 19:05:05 +0200
Manfred Spraul <[email protected]> wrote:
> Hi Andrew,
>
> poll() returns -EINTR if a signal is pending.
> EINTR is a bad choice: it means that poll returns to user space if the
> task is stopped by SIGSTOP/SIGCONT or by the freezer.
> select() and ppoll() both use ERESTARTNOHAND, this avoids a return to
> user space for signals that are handled by the kernel.
>
> The patch switches poll() to ERESTARTNOHAND.
> Tested with FC6. Patch against 2.6.23-rc1-mm1.
hm. Is this a fix against
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.23-rc1/2.6.23-rc1-mm1/broken-out/do_poll-return-eintr-when-signalled.patch
only, or does mainline also need fixing?
I guess the consequences of the thing-which-this-fixes aren't huge, s I ca
queue this up for 2.6.24, after Oleg's
do_poll-return-eintr-when-signalled.patch?
> Signed-off-by: Manfred Spraul <[email protected]>
>
> --- 2.6/fs/select.c 2007-07-28 20:31:51.000000000 +0200
> +++ build-2.6/fs/select.c 2007-07-28 21:21:52.000000000 +0200
> @@ -621,7 +621,7 @@ static int do_poll(unsigned int nfds, s
> if (!count) {
> count = wait->error;
> if (signal_pending(current))
> - count = -EINTR;
> + count = -ERESTARTNOHAND;
> }
> if (count || !*timeout)
> break;
> @@ -774,7 +774,7 @@ asmlinkage long sys_ppoll(struct pollfd
> ret = do_sys_poll(ufds, nfds, &timeout);
>
> /* We can restart this syscall, usually */
> - if (ret == -EINTR) {
> + if (ret == -ERESTARTNOHAND) {
> /*
> * Don't restore the signal mask yet. Let do_signal() deliver
> * the signal on the way back to userspace, before the signal
> @@ -785,7 +785,6 @@ asmlinkage long sys_ppoll(struct pollfd
> sizeof(sigsaved));
> set_thread_flag(TIF_RESTORE_SIGMASK);
> }
> - ret = -ERESTARTNOHAND;
> } else if (sigmask)
> sigprocmask(SIG_SETMASK, &sigsaved, NULL);
>
I spied this comment in there:
/*
* We can actually return ERESTARTSYS instead of EINTR, but I'd
* like to be certain this leads to no problems. So I return
* EINTR just for safety.
*
* Update: ERESTARTSYS breaks at least the xview clock binary, so
* I'm trying ERESTARTNOHAND which restart only when you want to.
*/
it is very old and perhaps is no longer relevant?
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