From: Rich Felker <dalias@libc.org>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Oleg Nesterov <oleg@redhat.com>,
linux-kernel@vger.kernel.org, libc-alpha@sourceware.org,
alistair23@gmail.com, ebiederm@xmission.com, arnd@arndb.de,
torvalds@linux-foundation.org, adhemerval.zanella@linaro.org,
fweimer@redhat.com, palmer@sifive.com, macro@wdc.com,
zongbox@gmail.com, akpm@linux-foundation.org,
viro@zeniv.linux.org.uk, hpa@zytor.com
Subject: Re: [PATCH v3 1/1] waitid: Add support for waiting for the current process group
Date: Wed, 14 Aug 2019 16:55:00 -0000 [thread overview]
Message-ID: <20190814165501.GJ9017@brightrain.aerifal.cx> (raw)
In-Reply-To: <20190814163443.6odsksff4jbta7be@wittgenstein>
On Wed, Aug 14, 2019 at 06:34:44PM +0200, Christian Brauner wrote:
> On Wed, Aug 14, 2019 at 06:15:17PM +0200, Christian Brauner wrote:
> > On Wed, Aug 14, 2019 at 06:09:17PM +0200, Oleg Nesterov wrote:
> > > On 08/14, Christian Brauner wrote:
> > > >
> > > > and a signal could come in between the system call that
> > > > retrieved the process gorup and the call to waitid that changes the
> > > ^^^^^
> > > > current process group.
> > >
> > > I noticed this typo only because I spent 2 minutes or more trying to
> > > understand this sentence ;) But yes, a signal handler or another thread
> >
> > I'll try to rewrite it. :)
>
> Ok, here's what I changed it to:
>
> It was recently discovered that the linux version of waitid is not a
> superset of the other wait functions because it does not include
> support for waiting for the current process group. This has two
> downsides:
> 1. An extra system call is needed to get the current process group.
> 2. After the current process group is received and before it is passed
> to waitid a signal could arrive causing the current process group to change.
I don't think "downsides" sufficiently conveys that this is hard
breakage of a requirement for waitpid. How about something like the
following?
"It was recently discovered that the linux version of waitid is not a
superset of the other wait functions because it does not include
support for waiting for the current process group. Userspace cannot
simply emulate this functionality with an additional getpgid syscall
due to inherent race conditions that violate the async-signal safety
requirements for waitpid."
Rich
next prev parent reply other threads:[~2019-08-14 16:55 UTC|newest]
Thread overview: 127+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 0:11 [RFC v3 00/23] RISC-V glibc port for the 32-bit Alistair Francis
2019-07-17 0:11 ` [RFC v3 08/23] RISC-V: define __NR_futex as __NR_futex_time64 for 32-bit Alistair Francis
2019-07-17 0:11 ` [RFC v3 03/23] sysdeps/wait: Use waitid if avaliable Alistair Francis
2019-07-17 5:31 ` Florian Weimer
2019-07-19 17:52 ` Alistair Francis
2019-07-22 15:58 ` Florian Weimer
2019-07-22 21:06 ` Alistair Francis
2019-07-21 4:03 ` Rich Felker
2019-07-21 4:20 ` Rich Felker
2019-07-21 11:59 ` Eric W. Biederman
2019-07-21 23:00 ` Rich Felker
2019-07-21 7:57 ` Arnd Bergmann
2019-07-21 12:15 ` Eric W. Biederman
2019-07-21 12:28 ` Christian Brauner
2019-07-21 14:31 ` Arnd Bergmann
2019-07-21 15:45 ` Eric W. Biederman
2019-07-21 17:06 ` Arnd Bergmann
2019-07-21 17:22 ` Linus Torvalds
2019-07-21 21:40 ` Eric W. Biederman
2019-07-21 23:24 ` Rich Felker
2019-07-23 0:01 ` Eric W. Biederman
2019-07-23 8:12 ` Arnd Bergmann
2019-07-23 8:29 ` Christian Brauner
2019-07-23 8:45 ` Arnd Bergmann
2019-07-25 0:08 ` Alistair Francis
2019-07-25 4:40 ` Rich Felker
2019-07-25 13:23 ` Arnd Bergmann
2019-07-25 16:06 ` Christian Brauner
2019-07-25 17:14 ` Eric W. Biederman
2019-07-25 17:30 ` Christian Brauner
2019-08-13 22:25 ` Alistair Francis
2019-08-13 23:12 ` Rich Felker
2019-08-14 5:07 ` Christian Brauner
2019-08-14 11:40 ` [PATCH v1 0/1] waitid: process group enhancement christian.brauner
2019-08-14 11:40 ` [PATCH v1 1/1] waitid: Add support for waiting for the current process group christian.brauner
2019-08-14 12:29 ` Oleg Nesterov
2019-08-14 12:46 ` Christian Brauner
2019-08-14 12:50 ` Oleg Nesterov
2019-08-14 12:53 ` Christian Brauner
2019-08-14 13:10 ` [PATCH v2 0/1] waitid: process group enhancement Christian Brauner
2019-08-14 13:10 ` [PATCH v2 1/1] waitid: Add support for waiting for the current process group Christian Brauner
2019-08-14 14:20 ` Oleg Nesterov
2019-08-14 14:35 ` Christian Brauner
2019-08-14 15:27 ` Oleg Nesterov
2019-08-14 15:30 ` Christian Brauner
2019-08-14 15:46 ` [PATCH v3 0/1] waitid: process group enhancement Christian Brauner
2019-08-14 15:46 ` [PATCH v3 1/1] waitid: Add support for waiting for the current process group Christian Brauner
2019-08-14 16:09 ` Oleg Nesterov
2019-08-14 16:15 ` Christian Brauner
2019-08-14 16:34 ` Christian Brauner
2019-08-14 16:55 ` Rich Felker [this message]
2019-08-14 17:02 ` Christian Brauner
2019-08-14 17:06 ` Linus Torvalds
2019-08-14 18:00 ` Rich Felker
2019-08-14 20:50 ` Christian Brauner
2019-08-14 15:58 ` [PATCH v3 0/1] waitid: process group enhancement Rich Felker
2019-08-14 16:13 ` Christian Brauner
2019-07-26 23:39 ` [RFC v3 03/23] sysdeps/wait: Use waitid if avaliable Alistair Francis
2019-07-17 0:11 ` [RFC v3 01/23] sysdeps/nanosleep: Use clock_nanosleep_time64 " Alistair Francis
2019-07-17 5:16 ` Florian Weimer
2019-07-19 17:29 ` Alistair Francis
2019-07-20 14:24 ` Stepan Golosunov
2019-07-22 21:17 ` Alistair Francis
2019-07-17 0:11 ` [RFC v3 02/23] sysdeps/gettimeofday: Use clock_gettime64 " Alistair Francis
2019-07-17 7:09 ` Florian Weimer
2019-07-20 3:21 ` Rich Felker
2019-07-25 20:54 ` Joseph Myers
2019-07-17 12:43 ` Lukasz Majewski
2019-07-17 12:48 ` Lukasz Majewski
2019-07-19 22:29 ` Alistair Francis
2019-07-17 0:11 ` [RFC v3 04/23] sysdeps/clock_gettime: " Alistair Francis
2019-07-17 5:39 ` Florian Weimer
2019-07-17 8:04 ` Arnd Bergmann
2019-07-17 8:44 ` Florian Weimer
2019-07-17 9:10 ` Arnd Bergmann
2019-07-17 15:16 ` Florian Weimer
2019-07-18 7:39 ` Arnd Bergmann
2019-07-18 8:19 ` Florian Weimer
2019-07-18 9:15 ` Arnd Bergmann
2019-07-18 18:10 ` Adhemerval Zanella
2019-07-19 21:06 ` Alistair Francis
2019-07-17 7:03 ` Andreas Schwab
2019-07-17 12:37 ` Lukasz Majewski
2019-07-17 0:12 ` [RFC v3 13/23] RISC-V: Use 64-bit timespec in clock_gettime vdso calls Alistair Francis
2019-07-17 8:14 ` Arnd Bergmann
2019-07-17 0:12 ` [RFC v3 14/23] RISC-V: Support dynamic loader for the 32-bit Alistair Francis
2019-07-17 0:12 ` [RFC v3 11/23] RISC-V: define __vdso_clock_getres as __vdso_clock_getres_time64 for 32-bit Alistair Francis
2019-07-17 0:12 ` [RFC v3 15/23] RISC-V: Add path of library directories for the 32-bit Alistair Francis
2019-07-17 12:20 ` Florian Weimer
2019-07-17 0:12 ` [RFC v3 12/23] RISC-V: define __vdso_clock_gettime as __vdso_clock_gettime64 for 32-bit Alistair Francis
2019-07-17 8:16 ` Arnd Bergmann
2019-07-19 17:19 ` Alistair Francis
2019-07-17 0:12 ` [RFC v3 10/23] RISC-V: define __NR_clock_getres as __NR_*_time64 " Alistair Francis
2019-07-17 0:12 ` [RFC v3 05/23] sysdeps/timespec_get: Use clock_gettime64 if avaliable Alistair Francis
2019-07-17 5:08 ` Florian Weimer
2019-07-17 7:59 ` Arnd Bergmann
2019-07-17 8:12 ` Florian Weimer
2019-07-17 8:23 ` Arnd Bergmann
2019-07-17 8:41 ` Florian Weimer
2019-07-17 8:54 ` Arnd Bergmann
2019-07-25 20:14 ` Joseph Myers
2019-07-17 12:23 ` Lukasz Majewski
2019-07-17 0:12 ` [RFC v3 21/23] RISC-V: Fix llrint and llround missing exceptions on RV32 Alistair Francis
2019-07-17 12:22 ` Florian Weimer
2019-07-17 22:35 ` Alistair Francis
2019-07-17 0:12 ` [RFC v3 22/23] Add RISC-V 32-bit target to build-many-glibcs.py Alistair Francis
2019-07-17 0:12 ` [RFC v3 16/23] RISC-V: The ABI implementation for the 32-bit Alistair Francis
2019-07-17 0:12 ` [RFC v3 06/23] Documentation for the RISC-V 32-bit port Alistair Francis
2019-07-17 0:12 ` [RFC v3 18/23] RISC-V: Regenerate ULPs of RISC-V Alistair Francis
2019-07-17 0:12 ` [RFC v3 07/23] RISC-V: Use 64-bit time_t and off_t for RV32 and RV64 Alistair Francis
2019-07-17 8:27 ` Arnd Bergmann
2019-07-17 22:43 ` Alistair Francis
2019-07-18 7:41 ` Arnd Bergmann
2019-07-18 17:36 ` Alistair Francis
2019-07-19 6:44 ` Arnd Bergmann
2019-07-19 17:06 ` Alistair Francis
2019-07-17 0:12 ` [RFC v3 17/23] RISC-V: Hard float support for the 32 bit Alistair Francis
2019-07-17 0:12 ` [RFC v3 20/23] RISC-V: Build Infastructure for the 32-bit Alistair Francis
2019-07-17 0:12 ` [RFC v3 23/23] RISC-V: Use 64-bit vdso syscalls Alistair Francis
2019-07-17 5:33 ` Florian Weimer
2019-07-17 8:02 ` Arnd Bergmann
2019-07-17 22:27 ` Alistair Francis
2019-07-17 23:46 ` Alistair Francis
2019-07-18 0:05 ` Alistair Francis
2019-07-17 0:12 ` [RFC v3 19/23] RISC-V: Add ABI lists Alistair Francis
2019-07-17 0:12 ` [RFC v3 09/23] RISC-V: define __NR_* as __NR_*_time64/64 for 32-bit Alistair Francis
2019-07-19 17:18 ` [RFC v3 00/23] RISC-V glibc port for the 32-bit Alistair Francis
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