From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> To: Oleg Nesterov <oleg@redhat.com> Cc: Andrey Wagin <avagin@gmail.com>, linux-kernel@vger.kernel.org, criu@openvz.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, Alexander Viro <viro@zeniv.linux.org.uk>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, David Howells <dhowells@redhat.com>, Dave Jones <davej@redhat.com>, Pavel Emelyanov <xemul@parallels.com>, Cyrill Gorcunov <gorcunov@openvz.org> Subject: Re: [PATCH 3/3] signalfd: add ability to read siginfo-s without dequeuing signals (v2) Date: Sat, 9 Feb 2013 23:53:04 +0100 [thread overview] Message-ID: <CAKgNAkiYrP046mEv1_GJED5DckJrZSHvwu2u=P_BRxx-NuKALQ@mail.gmail.com> (raw) In-Reply-To: <20130209182239.GA9947@redhat.com> On Sat, Feb 9, 2013 at 7:22 PM, Oleg Nesterov <oleg@redhat.com> wrote: > On 02/08, Michael Kerrisk (man-pages) wrote: >> >> On Fri, Feb 8, 2013 at 8:10 PM, Oleg Nesterov <oleg@redhat.com> wrote: >> > >> > Well. I do not know. Up to you and Michael. >> > >> > But honestly, I can't say this all looks really nice. And why do we >> > need SIGNALFD_PEEK then? >> >> It surely is no beauty. The hope is at least to make it less ugly than it was. > > This is subjective, but I am not sure about "less" ;) Yes, we avoid the > magic offsets, but we add SFD_SHARED/PER_THREAD which need to change > dequeue_signal plus other complications. And for what? > >> > Seriously, perhaps we should simply add signalfd_fops->ioctl() for PEEK. >> > Or add PTRACE_{PEEK,POKE}_SIGNAL which looks even logical and useful... >> > And much simpler/straightforward. >> > >> > But I am not going to argue. >> >> I suppose I had wondered along similar lines, but in a slightly >> different direction: would the use of a /proc interface to get the >> queued signals make some sense? > > (Can't resist sorry... yes we need /proc/pid/cr or /dev/cr or whatever > which dumps almost everything c/r needs without need to add a lot of > cr code everywhere). > > Perhaps, but I am not sure about the textual representation. > > And to me, the best solution is the simplest solution. Please look > at the patch below. It is trivial. And we can also drop the SFD_RAW > patch in -mm. Oleg, This looks promising, but I am not sure I understand the user-space API. Could you explain how it would look to (say) pull all per-thread signals from user space? Thanks, Michael > --- x/kernel/ptrace.c > +++ x/kernel/ptrace.c > @@ -618,6 +618,35 @@ static int ptrace_setsiginfo(struct task > return error; > } > > +static int ptrace_peek_signal(struct task_struct *child, > + unsigned long addr, siginfo_t __user *uinfo) > +{ > + siginfo_t info; > + struct sigpending *pending; > + int ret = -ESOMETHING; > + > + pending = &child->pending; > + if (addr & PTRACE_PEEK_SHARED) { > + addr &= ~PTRACE_PEEK_SHARED; > + pending = &child->signal->shared_pending; > + } > + > + spin_lock_irq(&child->sighand->siglock); > + list_for_each_entry(q, &pending->list, list) { > + if (!addr--) { > + copy_siginfo(info, &q->info); > + ret = 0; > + break; > + } > + } > + spin_lock_irq(&child->sighand->siglock); > + > + if (!ret) > + ret = copy_siginfo_to_user(uinfo, info); > + if (!ret) > + ret = __put_user(info, si_code); > + return ret; > +} > > #ifdef PTRACE_SINGLESTEP > #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP) > @@ -742,6 +771,10 @@ int ptrace_request(struct task_struct *c > ret = put_user(child->ptrace_message, datalp); > break; > > + case PTRACE_PEEKSIGNAL: > + ret = ptrace_peek_signal(child, addr, datavp); > + break; > + > case PTRACE_GETSIGINFO: > ret = ptrace_getsiginfo(child, &siginfo); > if (!ret) > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/
WARNING: multiple messages have this Message-ID (diff)
From: "Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> To: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Cc: Andrey Wagin <avagin-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, criu-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Alexander Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>, "Paul E. McKenney" <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Dave Jones <davej-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>, Cyrill Gorcunov <gorcunov-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org> Subject: Re: [PATCH 3/3] signalfd: add ability to read siginfo-s without dequeuing signals (v2) Date: Sat, 9 Feb 2013 23:53:04 +0100 [thread overview] Message-ID: <CAKgNAkiYrP046mEv1_GJED5DckJrZSHvwu2u=P_BRxx-NuKALQ@mail.gmail.com> (raw) In-Reply-To: <20130209182239.GA9947-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> On Sat, Feb 9, 2013 at 7:22 PM, Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote: > On 02/08, Michael Kerrisk (man-pages) wrote: >> >> On Fri, Feb 8, 2013 at 8:10 PM, Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote: >> > >> > Well. I do not know. Up to you and Michael. >> > >> > But honestly, I can't say this all looks really nice. And why do we >> > need SIGNALFD_PEEK then? >> >> It surely is no beauty. The hope is at least to make it less ugly than it was. > > This is subjective, but I am not sure about "less" ;) Yes, we avoid the > magic offsets, but we add SFD_SHARED/PER_THREAD which need to change > dequeue_signal plus other complications. And for what? > >> > Seriously, perhaps we should simply add signalfd_fops->ioctl() for PEEK. >> > Or add PTRACE_{PEEK,POKE}_SIGNAL which looks even logical and useful... >> > And much simpler/straightforward. >> > >> > But I am not going to argue. >> >> I suppose I had wondered along similar lines, but in a slightly >> different direction: would the use of a /proc interface to get the >> queued signals make some sense? > > (Can't resist sorry... yes we need /proc/pid/cr or /dev/cr or whatever > which dumps almost everything c/r needs without need to add a lot of > cr code everywhere). > > Perhaps, but I am not sure about the textual representation. > > And to me, the best solution is the simplest solution. Please look > at the patch below. It is trivial. And we can also drop the SFD_RAW > patch in -mm. Oleg, This looks promising, but I am not sure I understand the user-space API. Could you explain how it would look to (say) pull all per-thread signals from user space? Thanks, Michael > --- x/kernel/ptrace.c > +++ x/kernel/ptrace.c > @@ -618,6 +618,35 @@ static int ptrace_setsiginfo(struct task > return error; > } > > +static int ptrace_peek_signal(struct task_struct *child, > + unsigned long addr, siginfo_t __user *uinfo) > +{ > + siginfo_t info; > + struct sigpending *pending; > + int ret = -ESOMETHING; > + > + pending = &child->pending; > + if (addr & PTRACE_PEEK_SHARED) { > + addr &= ~PTRACE_PEEK_SHARED; > + pending = &child->signal->shared_pending; > + } > + > + spin_lock_irq(&child->sighand->siglock); > + list_for_each_entry(q, &pending->list, list) { > + if (!addr--) { > + copy_siginfo(info, &q->info); > + ret = 0; > + break; > + } > + } > + spin_lock_irq(&child->sighand->siglock); > + > + if (!ret) > + ret = copy_siginfo_to_user(uinfo, info); > + if (!ret) > + ret = __put_user(info, si_code); > + return ret; > +} > > #ifdef PTRACE_SINGLESTEP > #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP) > @@ -742,6 +771,10 @@ int ptrace_request(struct task_struct *c > ret = put_user(child->ptrace_message, datalp); > break; > > + case PTRACE_PEEKSIGNAL: > + ret = ptrace_peek_signal(child, addr, datavp); > + break; > + > case PTRACE_GETSIGINFO: > ret = ptrace_getsiginfo(child, &siginfo); > if (!ret) > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/
next prev parent reply other threads:[~2013-02-09 22:53 UTC|newest] Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-01-22 10:15 [PATCH 0/3] signalfd: a kernel interface for dumping pending signals Andrey Vagin 2013-01-22 10:15 ` Andrey Vagin 2013-01-22 10:15 ` [PATCH 1/3] signal: add a helper for dequeuing signals from a specified queue Andrey Vagin 2013-01-22 10:15 ` Andrey Vagin 2013-02-05 12:00 ` [PATCH 1/3] signal: add a helper for dequeuing signals from a specified queue (v2) Andrey Vagin 2013-02-05 12:00 ` Andrey Vagin 2013-01-22 10:15 ` [PATCH 2/3] signalfd: add ability to choose a private or shared queue Andrey Vagin 2013-01-22 10:15 ` Andrey Vagin 2013-02-07 18:17 ` Oleg Nesterov 2013-02-08 0:35 ` Michael Kerrisk (man-pages) 2013-02-08 0:35 ` Michael Kerrisk (man-pages) 2013-02-08 19:12 ` Oleg Nesterov 2013-01-22 10:15 ` [PATCH 3/3] signalfd: add ability to read siginfo-s without dequeuing signals Andrey Vagin 2013-01-29 19:03 ` [PATCH 3/3] signalfd: add ability to read siginfo-s without dequeuing signals (v2) Andrey Vagin [not found] ` <CAKgNAkgQA=zK=2ZnytPFU=DH6jr0sja0iy6K+j6c7unheLFniQ@mail.gmail.com> 2013-02-02 7:15 ` Andrey Wagin 2013-02-02 7:15 ` Andrey Wagin 2013-02-07 17:34 ` Oleg Nesterov 2013-02-07 17:34 ` Oleg Nesterov 2013-02-07 21:13 ` Andrey Wagin 2013-02-07 21:13 ` Andrey Wagin 2013-02-08 0:51 ` Michael Kerrisk (man-pages) 2013-02-08 19:10 ` Oleg Nesterov 2013-02-08 20:15 ` Michael Kerrisk (man-pages) 2013-02-08 20:15 ` Michael Kerrisk (man-pages) 2013-02-09 18:22 ` Oleg Nesterov 2013-02-09 22:53 ` Michael Kerrisk (man-pages) [this message] 2013-02-09 22:53 ` Michael Kerrisk (man-pages) 2013-02-10 10:04 ` [CRIU] " Andrew Vagin 2013-02-10 10:04 ` Andrew Vagin 2013-02-11 16:47 ` Oleg Nesterov 2013-02-11 16:47 ` Oleg Nesterov 2013-02-10 10:07 ` Andrew Vagin 2013-02-10 10:07 ` Andrew Vagin 2013-02-11 9:29 ` Denys Vlasenko 2013-02-11 10:59 ` [CRIU] " Andrew Vagin 2013-02-11 10:59 ` Andrew Vagin 2013-02-11 14:46 ` Denys Vlasenko 2013-02-11 14:46 ` Denys Vlasenko 2013-02-11 14:53 ` Pavel Emelyanov 2013-02-11 14:53 ` Pavel Emelyanov 2013-02-11 17:25 ` Denys Vlasenko 2013-02-11 17:25 ` Denys Vlasenko 2013-02-12 14:50 ` Pavel Emelyanov 2013-02-12 14:50 ` Pavel Emelyanov 2013-01-23 4:19 ` [PATCH 0/3] signalfd: a kernel interface for dumping pending signals Michael Kerrisk (man-pages) 2013-01-23 11:03 ` Andrew Vagin 2013-01-23 11:03 ` Andrew Vagin 2013-01-23 11:03 ` Andrew Vagin 2013-01-23 12:11 ` Michael Kerrisk (man-pages) 2013-01-23 12:11 ` Michael Kerrisk (man-pages) 2013-01-23 13:03 ` Andrew Vagin 2013-01-23 13:03 ` Andrew Vagin 2013-01-23 13:03 ` Andrew Vagin 2013-02-07 18:20 ` Oleg Nesterov 2013-02-07 18:20 ` Oleg Nesterov 2013-02-08 0:36 ` Michael Kerrisk (man-pages) 2013-02-08 0:36 ` Michael Kerrisk (man-pages)
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