From: Al Viro <viro@ZenIV.linux.org.uk>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
Russell King <linux@arm.linux.org.uk>, Tejun Heo <tj@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Roland McGrath <roland@hack.frob.com>
Subject: Re: [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such
Date: Wed, 25 Apr 2012 18:51:13 +0100 [thread overview]
Message-ID: <20120425175113.GI6871@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20120425170230.GA24977@redhat.com>
On Wed, Apr 25, 2012 at 07:02:30PM +0200, Oleg Nesterov wrote:
> And there is another case:
>
> syscall interrupted, it returns ERESTARTSYS.
>
> do_signal() sees no signal, restarts the syscall
>
> !SA_RESTART comes before we return to user-mode
>
> This doesn't really differ from sigsuspend/ERESTARTNOHAND we discussed
> before.
... and dealt with the same way:
NEED_RESTART flag is set the first time around
no handler for the first signal, so we do nothing else
handler is found for the second signal
NEED_RESTART flag is present, so
we clear NEED_RESTART
we look at errno and see ERESTARTSYS
we check sa_flags and see !SA_RESTART
we set return value to -EINTR and proceed to set sigframe up
on the exit to userland we see NEED_RESTART not set, so off we go
I think I hadn't been clear enough; here's pseudocode for what I meant
do_signal()
{
if (we have any business doing restarts)
// note: we won't get here on subsequent calls of do_signal()
// due to the checks above; same logics that currently prevents
// double restarts
set NEED_RESTART flag
sig = get_signal_to_deliver(...)
if (sig) {
if (NEED_RESTART set) {
clear NEED_RESTART
same thing we do at that spot now - restart or EINTR
handle_signal(...)
...
return;
}
}
/* no handler */
if (test_and_clear_...(RESTORE_SIGMASK))
set_current_blocked(¤t->saved_sigmask);
}
and in asm glue, *after* checking for SIGPENDING/NOTIFY_RESUME, check
NEED_RESTART and if it's set do what we currently do for restarts on
handlerless signal.
BTW, if we combine that with ERESTART_RESTARTBLOCK trick on arm/parisc/unicore,
there won't be much work to do for restarts in that case; in x86ese it
would be simply
if (regs->ax == -ERESTART_RESTARTBLOCK)
set_thread_flag(TIF_EMULATE_RESTART_SYSCALL)
regs->ax = regs->orig_ax;
regs->ip -= 2;
all of that conditional on TS_NEED_RESTART...
next prev parent reply other threads:[~2012-04-25 17:51 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-18 13:04 [PULL REQUEST] : ima-appraisal patches Mimi Zohar
2012-04-18 15:02 ` James Morris
2012-04-18 18:07 ` Mimi Zohar
2012-04-18 18:39 ` Al Viro
2012-04-18 20:56 ` Mimi Zohar
2012-04-19 19:57 ` Mimi Zohar
2012-04-20 0:43 ` [RFC] situation with fput() locking (was Re: [PULL REQUEST] : ima-appraisal patches) Al Viro
2012-04-20 2:31 ` Linus Torvalds
2012-04-20 2:31 ` Linus Torvalds
2012-04-20 2:54 ` Al Viro
2012-04-20 2:58 ` Linus Torvalds
2012-04-20 2:58 ` Linus Torvalds
2012-04-20 8:09 ` Al Viro
2012-04-20 15:56 ` Linus Torvalds
2012-04-20 15:56 ` Linus Torvalds
2012-04-20 16:08 ` Al Viro
2012-04-20 16:42 ` Al Viro
2012-04-20 17:21 ` Linus Torvalds
2012-04-20 17:21 ` Linus Torvalds
2012-04-20 18:07 ` Al Viro
2012-04-23 18:01 ` [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such Al Viro
2012-04-23 18:37 ` Oleg Nesterov
2012-04-24 7:26 ` Al Viro
2012-04-25 3:06 ` Al Viro
2012-04-25 12:37 ` Oleg Nesterov
2012-04-25 12:50 ` Al Viro
2012-04-25 13:03 ` Oleg Nesterov
2012-04-25 13:32 ` Oleg Nesterov
2012-04-25 13:32 ` Al Viro
2012-04-25 14:52 ` Oleg Nesterov
2012-04-25 15:46 ` Oleg Nesterov
2012-04-25 16:10 ` Al Viro
2012-04-25 17:02 ` Oleg Nesterov
2012-04-25 17:51 ` Al Viro [this message]
2012-04-26 7:15 ` Martin Schwidefsky
2012-04-26 7:25 ` David Miller
2012-04-26 13:52 ` Oleg Nesterov
2012-04-26 14:31 ` Martin Schwidefsky
2012-04-26 13:22 ` Oleg Nesterov
2012-04-26 18:37 ` Oleg Nesterov
2012-04-26 23:19 ` Al Viro
2012-04-27 17:24 ` Oleg Nesterov
2012-04-27 17:54 ` Oleg Nesterov
2012-05-02 10:37 ` Matt Fleming
2012-05-02 14:14 ` Al Viro
2012-04-27 18:45 ` Al Viro
2012-04-27 19:14 ` Geert Uytterhoeven
2012-04-27 19:34 ` Al Viro
2012-04-29 22:51 ` Al Viro
2012-04-30 6:39 ` Greg Ungerer
2012-04-30 6:39 ` Greg Ungerer
2012-04-27 19:42 ` Al Viro
2012-04-27 20:20 ` Roland McGrath
2012-04-27 21:12 ` Al Viro
2012-04-27 21:27 ` Roland McGrath
2012-04-27 23:15 ` Al Viro
2012-04-27 23:32 ` Al Viro
2012-04-29 4:12 ` Al Viro
2012-04-30 8:06 ` Martin Schwidefsky
2012-04-27 23:50 ` Al Viro
2012-04-28 18:51 ` [PATCH] arch/tile: avoid calling do_signal() after fork from a kernel thread Chris Metcalf
2012-04-28 18:51 ` Chris Metcalf
2012-04-28 20:55 ` Al Viro
2012-04-28 21:46 ` Chris Metcalf
2012-04-28 21:46 ` Chris Metcalf
2012-04-29 0:55 ` Al Viro
2012-04-28 18:51 ` [PATCH v2] arch/tile: fix up some issues in calling do_work_pending() Chris Metcalf
2012-04-28 18:51 ` Chris Metcalf
2012-04-29 3:49 ` [PATCH] arch/tile: avoid calling do_signal() after fork from a kernel thread Chris Metcalf
2012-04-29 3:49 ` Chris Metcalf
2012-04-28 2:42 ` [RFC] TIF_NOTIFY_RESUME, arch/*/*/*signal*.c and all such Al Viro
2012-04-28 3:32 ` Al Viro
2012-04-28 3:36 ` Al Viro
2012-04-29 16:33 ` Oleg Nesterov
2012-04-29 16:18 ` Oleg Nesterov
2012-04-29 18:05 ` Al Viro
2012-05-01 4:31 ` Al Viro
2012-05-01 5:06 ` Mike Frysinger
2012-05-01 5:52 ` Al Viro
2012-05-02 17:24 ` Al Viro
2012-05-02 18:30 ` Oleg Nesterov
2012-04-29 16:41 ` Oleg Nesterov
2012-04-29 18:09 ` Al Viro
2012-04-29 18:25 ` Oleg Nesterov
2012-04-20 3:15 ` [RFC] situation with fput() locking (was Re: [PULL REQUEST] : ima-appraisal patches) Al Viro
2012-04-20 18:54 ` Hugh Dickins
2012-04-20 19:04 ` Al Viro
2012-04-20 19:18 ` Linus Torvalds
2012-04-20 19:32 ` Hugh Dickins
2012-04-20 19:58 ` Al Viro
2012-04-20 21:12 ` Linus Torvalds
2012-04-20 21:12 ` Linus Torvalds
2012-04-20 22:13 ` Al Viro
2012-04-20 22:35 ` Linus Torvalds
2012-04-20 22:35 ` Linus Torvalds
2012-04-27 7:35 ` Kasatkin, Dmitry
2012-04-27 17:34 ` Al Viro
2012-04-27 18:52 ` Kasatkin, Dmitry
2012-04-27 18:52 ` Kasatkin, Dmitry
2012-04-27 19:15 ` Kasatkin, Dmitry
2012-04-30 14:32 ` Mimi Zohar
2012-04-30 14:32 ` Mimi Zohar
2012-05-03 4:23 ` James Morris
2012-05-03 4:23 ` James Morris
2012-04-20 19:37 ` Al Viro
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