From: Deepa Dinamani <deepa.kernel@gmail.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Arnd Bergmann <arnd@arndb.de>,
dbueso@suse.de, axboe@kernel.dk,
Davidlohr Bueso <dave@stgolabs.net>, Eric Wong <e@80x24.org>,
Jason Baron <jbaron@akamai.com>,
Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
linux-aio <linux-aio@kvack.org>,
Omar Kilani <omar.kilani@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
stable@vger.kernel.org
Subject: Re: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask()
Date: Wed, 22 May 2019 09:33:50 -0700 [thread overview]
Message-ID: <CABeXuvpjrW5Gt95JC-_rYkOA=6RCD5OtkEQdwZVVqGCE3GkQOQ@mail.gmail.com> (raw)
In-Reply-To: <20190522161407.GB4915@redhat.com>
On Wed, May 22, 2019 at 9:14 AM Oleg Nesterov <oleg@redhat.com> wrote:
>
> On 05/22, Deepa Dinamani wrote:
> >
> > -Deepa
> >
> > > On May 22, 2019, at 8:05 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> > >
> > >> On 05/21, Deepa Dinamani wrote:
> > >>
> > >> Note that this patch returns interrupted errors (EINTR, ERESTARTNOHAND,
> > >> etc) only when there is no other error. If there is a signal and an error
> > >> like EINVAL, the syscalls return -EINVAL rather than the interrupted
> > >> error codes.
> > >
> > > Ugh. I need to re-check, but at first glance I really dislike this change.
> > >
> > > I think we can fix the problem _and_ simplify the code. Something like below.
> > > The patch is obviously incomplete, it changes only only one caller of
> > > set_user_sigmask(), epoll_pwait() to explain what I mean.
> > > restore_user_sigmask() should simply die. Although perhaps another helper
> > > makes sense to add WARN_ON(test_tsk_restore_sigmask() && !signal_pending).
> >
> > restore_user_sigmask() was added because of all the variants of these
> > syscalls we added because of y2038 as noted in commit message:
> >
> > signal: Add restore_user_sigmask()
> >
> > Refactor the logic to restore the sigmask before the syscall
> > returns into an api.
> > This is useful for versions of syscalls that pass in the
> > sigmask and expect the current->sigmask to be changed during
> > the execution and restored after the execution of the syscall.
> >
> > With the advent of new y2038 syscalls in the subsequent patches,
> > we add two more new versions of the syscalls (for pselect, ppoll
> > and io_pgetevents) in addition to the existing native and compat
> > versions. Adding such an api reduces the logic that would need to
> > be replicated otherwise.
>
> Again, I need to re-check, will continue tomorrow. But so far I am not sure
> this helper can actually help.
>
> > > --- a/fs/eventpoll.c
> > > +++ b/fs/eventpoll.c
> > > @@ -2318,19 +2318,19 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
> > > size_t, sigsetsize)
> > > {
> > > int error;
> > > - sigset_t ksigmask, sigsaved;
> > >
> > > /*
> > > * If the caller wants a certain signal mask to be set during the wait,
> > > * we apply it here.
> > > */
> > > - error = set_user_sigmask(sigmask, &ksigmask, &sigsaved, sigsetsize);
> > > + error = set_user_sigmask(sigmask, sigsetsize);
> > > if (error)
> > > return error;
> > >
> > > error = do_epoll_wait(epfd, events, maxevents, timeout);
> > >
> > > - restore_user_sigmask(sigmask, &sigsaved);
> > > + if (error != -EINTR)
> >
> > As you address all the other syscalls this condition becomes more and
> > more complicated.
>
> May be.
>
> > > --- a/include/linux/sched/signal.h
> > > +++ b/include/linux/sched/signal.h
> > > @@ -416,7 +416,6 @@ void task_join_group_stop(struct task_struct *task);
> > > static inline void set_restore_sigmask(void)
> > > {
> > > set_thread_flag(TIF_RESTORE_SIGMASK);
> > > - WARN_ON(!test_thread_flag(TIF_SIGPENDING));
> >
> > So you always want do_signal() to be called?
>
> Why do you think so? No. This is just to avoid the warning, because with the
> patch I sent set_restore_sigmask() is called "in advance".
>
> > You will have to check each architecture's implementation of
> > do_signal() to check if that has any side effects.
>
> I don't think so.
Why not?
> > Although this is not what the patch is solving.
>
> Sure. But you know, after I tried to read the changelog, I am not sure
> I understand what exactly you are trying to fix. Could you please explain
> this part
>
> The behavior
> before 854a6ed56839a was that the signals were dropped after the error
> code was decided. This resulted in lost signals but the userspace did not
> notice it
>
> ? I fail to understand it, sorry. It looks as if the code was already buggy before
> that commit and it could miss a signal or something like this, but I do not see how.
Did you read the explanation pointed to in the commit text? :
https://lore.kernel.org/linux-fsdevel/20190427093319.sgicqik2oqkez3wk@dcvr/
Let me know what part you don't understand and I can explain more.
It would be better to understand the isssue before we start discussing the fix.
-Deepa
next prev parent reply other threads:[~2019-05-22 16:34 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 3:21 [PATCH v2] signal: Adjust error codes according to restore_user_sigmask() Deepa Dinamani
2019-05-22 15:05 ` Oleg Nesterov
2019-05-22 15:55 ` Deepa Dinamani
2019-05-22 16:14 ` Oleg Nesterov
2019-05-22 16:33 ` Deepa Dinamani [this message]
2019-05-23 9:03 ` David Laight
2019-05-23 14:59 ` Oleg Nesterov
2019-05-23 16:18 ` David Laight
2019-05-23 16:36 ` Oleg Nesterov
2019-05-23 16:56 ` David Laight
2019-05-23 18:06 ` Deepa Dinamani
2019-05-23 20:41 ` Deepa Dinamani
2019-05-23 21:06 ` Deepa Dinamani
2019-05-24 9:58 ` David Laight
2019-05-24 14:10 ` Oleg Nesterov
2019-05-24 15:16 ` Deepa Dinamani
2019-05-24 16:33 ` Oleg Nesterov
2019-05-24 17:01 ` Deepa Dinamani
2019-05-27 15:04 ` Oleg Nesterov
2019-05-28 20:47 ` Deepa Dinamani
2019-05-29 16:57 ` Oleg Nesterov
2019-05-29 18:42 ` Deepa Dinamani
2019-05-28 9:02 ` David Laight
2019-05-28 9:12 ` David Laight
2019-05-28 11:37 ` Deepa Dinamani
2019-05-28 12:04 ` David Laight
2019-05-24 14:19 ` Oleg Nesterov
2019-05-24 14:29 ` Deepa Dinamani
2019-05-24 14:51 ` Oleg Nesterov
2019-05-24 13:29 ` Oleg Nesterov
2019-05-24 14:59 ` David Laight
2019-05-24 15:09 ` David Laight
2019-05-24 15:46 ` Oleg Nesterov
2019-05-24 15:44 ` Oleg Nesterov
2019-05-24 16:40 ` David Laight
2019-05-23 14:33 ` Oleg Nesterov
2019-05-22 22:18 ` Chris Down
2019-05-22 22:52 ` Deepa Dinamani
2019-05-29 16:11 ` pselect/etc semantics (Was: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask()) Oleg Nesterov
2019-05-29 16:54 ` David Laight
2019-05-29 18:50 ` Eric Wong
2019-05-30 9:34 ` David Laight
2019-05-30 13:04 ` pselect/etc semantics Eric W. Biederman
2019-05-29 16:56 ` pselect/etc semantics (Was: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask()) Deepa Dinamani
2019-05-29 18:26 ` Deepa Dinamani
2019-05-29 22:32 ` Arnd Bergmann
2019-05-30 1:54 ` pselect/etc semantics Eric W. Biederman
2019-05-30 18:28 ` Arnd Bergmann
2019-05-30 14:40 ` pselect/etc semantics (Was: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask()) Oleg Nesterov
2019-05-30 18:37 ` Arnd Bergmann
2019-05-30 13:01 ` pselect/etc semantics Eric W. Biederman
2019-05-30 15:18 ` David Laight
2019-05-30 16:13 ` Oleg Nesterov
2019-05-30 15:38 ` Eric W. Biederman
2019-05-30 15:48 ` Deepa Dinamani
2019-05-30 16:59 ` Deepa Dinamani
2019-05-30 16:08 ` Oleg Nesterov
2019-05-30 17:20 ` Eric W. Biederman
2019-05-30 16:22 ` David Laight
2019-05-30 15:57 ` Oleg Nesterov
2019-05-30 21:03 ` Eric Wong
2019-06-04 13:41 ` [PATCH] signal: remove the wrong signal_pending() check in restore_user_sigmask() Oleg Nesterov
2019-06-04 15:31 ` Eric W. Biederman
2019-06-04 15:57 ` David Laight
2019-06-04 16:37 ` Arnd Bergmann
2019-06-04 18:14 ` Deepa Dinamani
2019-06-04 18:35 ` Eric Wong
2019-06-04 21:26 ` Linus Torvalds
2019-06-04 22:24 ` Eric Wong
2019-06-04 23:51 ` Eric W. Biederman
2019-06-05 9:04 ` Oleg Nesterov
2019-06-05 8:56 ` Oleg Nesterov
2019-06-05 9:02 ` David Laight
2019-06-05 9:25 ` Oleg Nesterov
2019-06-05 9:58 ` David Laight
2019-06-05 15:58 ` [PATCH -mm 0/1] signal: simplify set_user_sigmask/restore_user_sigmask Oleg Nesterov
2019-06-05 15:58 ` [PATCH -mm 1/1] " Oleg Nesterov
2019-06-06 0:14 ` kbuild test robot
2019-06-06 1:06 ` kbuild test robot
2019-06-06 7:25 ` Oleg Nesterov
2019-06-06 7:30 ` Sedat Dilek
2019-06-05 17:24 ` [PATCH -mm 0/1] " Linus Torvalds
2019-06-06 9:05 ` David Laight
2019-06-06 11:05 ` Oleg Nesterov
2019-06-06 11:29 ` David Laight
2019-06-06 12:41 ` Oleg Nesterov
2019-06-06 13:23 ` David Laight
2019-06-06 10:22 ` Oleg Nesterov
2019-06-06 11:32 ` [PATCH -mm V2 1/1] " Oleg Nesterov
2019-06-06 14:08 ` [PATCH 0/2] select: simplify the usage of restore_saved_sigmask_unless() Oleg Nesterov
2019-06-06 14:08 ` [PATCH 1/2] select: change do_poll() to return -ERESTARTNOHAND rather than -EINTR Oleg Nesterov
2019-06-07 18:05 ` Linus Torvalds
2019-06-06 14:09 ` [PATCH 2/2] select: shift restore_saved_sigmask_unless() into poll_select_copy_remaining() Oleg Nesterov
2019-06-07 21:39 ` [RFC PATCH 0/5]: Removing saved_sigmask Eric W. Biederman
2019-06-11 18:58 ` Oleg Nesterov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CABeXuvpjrW5Gt95JC-_rYkOA=6RCD5OtkEQdwZVVqGCE3GkQOQ@mail.gmail.com' \
--to=deepa.kernel@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=axboe@kernel.dk \
--cc=dave@stgolabs.net \
--cc=dbueso@suse.de \
--cc=e@80x24.org \
--cc=jbaron@akamai.com \
--cc=linux-aio@kvack.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=oleg@redhat.com \
--cc=omar.kilani@gmail.com \
--cc=stable@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).