From: Florian Weimer <fweimer@redhat.com>
To: Christian Brauner <brauner@kernel.org>
Cc: "André Almeida" <andrealmeid@igalia.com>,
"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
"Paul E . McKenney" <paulmck@kernel.org>,
"Boqun Feng" <boqun.feng@gmail.com>,
"H . Peter Anvin" <hpa@zytor.com>, "Paul Turner" <pjt@google.com>,
linux-api@vger.kernel.org, David.Laight@aculab.com,
carlos@redhat.com, "Peter Oskolkov" <posk@posk.io>,
"Alexander Mikhalitsyn" <alexander@mihalicyn.com>,
"Chris Kennelly" <ckennelly@google.com>,
"Ingo Molnar" <mingo@redhat.com>,
"Darren Hart" <dvhart@infradead.org>,
"Davidlohr Bueso" <dave@stgolabs.net>,
libc-alpha@sourceware.org, "Steven Rostedt" <rostedt@goodmis.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"Noah Goldstein" <goldstein.w.n@gmail.com>,
"Daniel Colascione" <dancol@google.com>,
longman@redhat.com, kernel-dev@igalia.com
Subject: Re: [RFC PATCH 0/1] Add FUTEX_SPIN operation
Date: Thu, 02 May 2024 11:51:56 +0200 [thread overview]
Message-ID: <8734r0o81v.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <20240502-gezeichnet-besonderen-d277879cd669@brauner> (Christian Brauner's message of "Thu, 2 May 2024 10:45:41 +0200")
* Christian Brauner:
> Unless I'm missing something the question here is PID (as in TGID aka
> thread-group leader id gotten via getpid()) vs TID (thread specific id
> gotten via gettid()). You want the thread-specific id as you want to
> interact with the futex state of a specific thread not the thread-group
> leader.
>
> Aside from that TIDs are subject to the same race conditions that PIDs
> are. They are allocated from the same pool (see alloc_pid()).
For most mutex types (but not robust mutexes), it is undefined in
userspace if a thread exits while it has locked a mutex. Such a usage
condition would ensure that the race doesn't happen, I believe.
From a glibc perspective, we typically cannot use long-term file
descriptors (that are kept open across function calls) because some
applications do not expect them, or even close them behind our back.
Thanks,
Florian
next prev parent reply other threads:[~2024-05-02 9:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-25 20:43 [RFC PATCH 0/1] Add FUTEX_SPIN operation André Almeida
2024-04-25 20:43 ` [RFC PATCH 1/1] futex: " André Almeida
2024-04-26 9:43 ` [RFC PATCH 0/1] " Florian Weimer
2024-04-26 10:14 ` Peter Zijlstra
2024-04-26 10:26 ` Christian Brauner
2024-05-01 23:44 ` André Almeida
2024-05-02 8:45 ` Christian Brauner
2024-05-02 9:51 ` Florian Weimer [this message]
2024-05-02 10:14 ` Christian Brauner
2024-05-02 10:39 ` Florian Weimer
2024-05-02 13:08 ` Christian Brauner
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