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Thu, 16 May 2019 15:23:01 +0000 (UTC) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190516_082301_566766_85CD4E89 X-CRM114-Status: GOOD ( 16.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, linux-mips@vger.kernel.org, dhowells@redhat.com, joel@joelfernandes.org, linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, linux-api@vger.kernel.org, elena.reshetova@intel.com, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, dancol@google.com, Geert Uytterhoeven , Christian Brauner , serge@hallyn.com, linux-xtensa@linux-xtensa.org, keescook@chromium.org, arnd@arndb.de, jannh@google.com, linux-m68k@lists.linux-m68k.org, viro@zeniv.linux.org.uk, luto@kernel.org, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, luto@amacapital.net, ebiederm@xmission.com, linux-alpha@vger.kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 05/17, Aleksa Sarai wrote: > > On 2019-05-16, Oleg Nesterov wrote: > > On 05/17, Aleksa Sarai wrote: > > > On 2019-05-16, Oleg Nesterov wrote: > > > > On 05/16, Christian Brauner wrote: > > > > > With the introduction of pidfds through CLONE_PIDFD it is possible to > > > > > created pidfds at process creation time. > > > > > > > > Now I am wondering why do we need CLONE_PIDFD, you can just do > > > > > > > > pid = fork(); > > > > pidfd_open(pid); > > > > > > While the race window would be exceptionally short, there is the > > > possibility that the child will die > > > > Yes, > > > > > and their pid will be recycled > > > before you do pidfd_open(). > > > > No. > > > > Unless the caller's sub-thread does wait() before pidfd_open(), of course. > > Or unless you do signal(SIGCHILD, SIG_IGN). > > What about CLONE_PARENT? I should have mentioned CLONE_PARENT ;) Of course in this case the child can be reaped before pidfd_open(). But how often do you or other people use clone(CLONE_PARENT) ? not to mention you can trivially eliminate/detect this race if you really need this. Don't get me wrong, I am not trying to say that CLONE_PIDFD is a bad idea. But to me pidfd_open() is much more useful. Say, as a perl programmer I can easily use pidfd_open(), but not CLONE_PIDFD. Oleg. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel