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From:   valdis.kletnieks@vt.edu
To:     ebiederm@xmission.com (Eric W. Biederman)
Cc:     Enke Chen <enkechen@cisco.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Khalid Aziz <khalid.aziz@oracle.com>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        Helge Deller <deller@gmx.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christian Brauner <christian@brauner.io>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Michal Hocko <mhocko@kernel.org>,
        Rik van Riel <riel@surriel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Roman Gushchin <guro@fb.com>,
        Marcos Paulo de Souza <marcos.souza.org@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Cyrill Gorcunov <gorcunov@openvz.org>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Jann Horn <jannh@google.com>,
        Kees Cook <keescook@chromium.org>,
        linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
        "Victor Kamensky \(kamensky\)" <kamensky@cisco.com>,
        xe-linux-external@cisco.com, Stefan Strogin <sstrogin@cisco.com>
Subject: Re: [PATCH] kernel/signal: Signal-based pre-coredump notification
In-Reply-To: <87va62lri4.fsf@xmission.com>
References: <e7ed306f-8992-9d00-bcab-5131159e8d89@cisco.com>
 <87va62lri4.fsf@xmission.com>
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Date:   Mon, 15 Oct 2018 20:33:51 -0400
Message-ID: <5192.1539650031@turing-police.cc.vt.edu>
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On Mon, 15 Oct 2018 18:28:03 -0500, Eric W. Biederman said:
> Enke Chen <enkechen@cisco.com> writes:
>
> > For simplicity and consistency, this patch provides an implementation
> > for signal-based fault notification prior to the coredump of a child
> > process. A new prctl command, PR_SET_PREDUMP_SIG, is defined that can
> > be used by an application to express its interest and to specify the
> > signal (SIGCHLD or SIGUSR1 or SIGUSR2) for such a notification. A new
> > signal code (si_code), CLD_PREDUMP, is also defined for SIGCHLD.
> >
> > Background:
> >
> > As the coredump of a process may take time, in certain time-sensitive
> > applications it is necessary for a parent process (e.g., a process
> > manager) to be notified of a child's imminent death before the coredump
> > so that the parent process can act sooner, such as re-spawning an
> > application process, or initiating a control-plane fail-over.
>
> You talk about time senstive and then you talk about bash scripts.
> I don't think your definition of time-sensitive and my definition match.

When the process image is measured in hundreds of gigabytes, the corefile can
take a while even by /bin/bash standards.  You want fun, watch an HPC process
manage to OOM a machine with 3T of RAM in a way that produces a full image
coredump.

To network storage.


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