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Howlett" , Suren Baghdasaryan , Vlastimil Babka , pedro.falcato@gmail.com, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/3] introduce PIDFD_SELF In-Reply-To: (Lorenzo Stoakes's message of "Mon, 30 Sep 2024 10:22:27 +0100") References: Date: Mon, 30 Sep 2024 12:33:18 +0200 Message-ID: <87ttdxl9ch.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-Rspamd-Queue-Id: 87C94A000B X-Stat-Signature: ryozb41fqzzop79zie1y88mequgaairt X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1727692414-276742 X-HE-Meta: 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 jpO92XcB QAe9FbNdecZy29/6mgJYZR7xwMtRfgWH+rH7WFNsLVOFyRUPVTiIDoEQ31qEX99syoedRIJ3jlIoh920xR4ZONAu8PLQH7jVe971cBk0vGA+6w+J+LKIkIQyC3wr0HfQCiKskm/HNRcHAPb6TmrPupiyfeDjvUy3e6sAS2lpO0YBz5unyiY3dD2WZ5a02xahdULmRytVkGg/Hx6QMEPe752bMd3JY0SBJRstaohf21YNAGZBlC1pB/BoW+CDJ/f/R91IawlTuqdoF1y2rx+W0F61Rmo53ZPy+x9QvxSBM43MXZuRjsaFh0LvyyuzyXF94bpopGQFT3ci9sDvCCiE72m7VQQrtrsdb4rtR X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: * Lorenzo Stoakes: > If you wish to utilise a pidfd interface to refer to the current process > (from the point of view of userland - from the kernel point of view - the > thread group leader), it is rather cumbersome, requiring something like: > > int pidfd = pidfd_open(getpid(), 0); > > ... > > close(pidfd); > > Or the equivalent call opening /proc/self. It is more convenient to use a > sentinel value to indicate to an interface that accepts a pidfd that we > simply wish to refer to the current process. The descriptor will refer to the current thread, not process, right? The distinction matters for pidfd_getfd if a process contains multiple threads with different file descriptor tables, and probably for pidfd_send_signal as well. Thanks, Florian