From nobody Mon Feb 9 23:41:56 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AC9521F8ADB for ; Tue, 3 Dec 2024 16:43:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733244221; cv=none; b=M1+UyrQJB4vHVN049ZJhr1v4bFSyG6GCZTQsRnasurF7ptlkNPCimHqnCYOJ3HIId4FDcBuuAiXn7lvwThgjIzoAFaopcisgr3lPRCE6EchKEuv/jsZRITz3HJXjXJTUA7NmfqkknDjLWacob/3zn02ycd4ZMp72PBjMDm/KjK8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733244221; c=relaxed/simple; bh=1jg7C4Hn7tl+DNFyCMZ58uFZgzsrwganhgb1pjnKjCs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ea6hWGAOdQLOZZxof4+TDFOlHWs5Al4J0GgoZzJWAjq0usi3kumsXwP7U6x2+95ZPY6xBXz7OS2vHugUxQ8ZaGrOkhvTgd6S786do8fbm0eZK5LhhYDmPc6ggCxSedWPu1x5zP1Z5cVwj6/TPu5noWVAXR3qCgjYYygvZYC76HU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=fiLfMQae; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=Fwj48aWp; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="fiLfMQae"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Fwj48aWp" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1733244218; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BZ1YXfG8xZyG1QlATAkQFmGyYAn75aCDQCDdTpLb2R8=; b=fiLfMQaeTXwX5dGNyPra8Hg97O74thVcC2fy8zPFrM8uWth3ZNUPkgzq9dMrG+xiezf6yS a17KkI4QFjkGDuNr1OHQdW+MItu9dYNCnMqxM1Eqtn9V2EO0zDibxt6APOf4nuB/dnAwJ2 P2J+VGsxJ2JyEoIz8bHSruC8cF6XK/PrsmO7fDlv8r25hd7jYJfYwDonk3uRYo2FG4cYo5 mqtPD6nnvnyaw7zWieCyRGbcOW7WkFH2fMOAN41amxT5wzGDHWUk80ZQbLo08Iu66vrHJw rONFgtAne5uereZvnq+r6Daj5ciwruOfHxAOMEWsAHLWK6e9na87qAh0EtIuYQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1733244218; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BZ1YXfG8xZyG1QlATAkQFmGyYAn75aCDQCDdTpLb2R8=; b=Fwj48aWpDnaqEvQJgYqkNOI5wai4nHTteDqyWcouVSpbmSuce2B9NicOMoJ0fhoxsn1DWJ 8CFUaXkZg07LuCCg== To: linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Andr=C3=A9=20Almeida?= , Darren Hart , Davidlohr Bueso , Ingo Molnar , Juri Lelli , Peter Zijlstra , Thomas Gleixner , Valentin Schneider , Waiman Long , Sebastian Andrzej Siewior Subject: [PATCH v4 03/11] futex: Allow automatic allocation of process wide futex hash. Date: Tue, 3 Dec 2024 17:42:11 +0100 Message-ID: <20241203164335.1125381-4-bigeasy@linutronix.de> In-Reply-To: <20241203164335.1125381-1-bigeasy@linutronix.de> References: <20241203164335.1125381-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Allocate a default futex hash if a task forks its first thread. Signed-off-by: Sebastian Andrzej Siewior --- kernel/fork.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/kernel/fork.c b/kernel/fork.c index cda8886f3a1d7..6267d600af991 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2130,6 +2130,17 @@ static void rv_task_fork(struct task_struct *p) #define rv_task_fork(p) do {} while (0) #endif =20 +static bool need_futex_hash_allocate_default(u64 clone_flags) +{ + if ((clone_flags & (CLONE_THREAD | CLONE_VM)) !=3D (CLONE_THREAD | CLONE_= VM)) + return false; + if (!thread_group_empty(current)) + return false; + if (current->mm->futex_hash_bucket) + return false; + return true; +} + /* * This creates a new process as a copy of the old one, * but does not actually start it yet. @@ -2507,6 +2518,21 @@ __latent_entropy struct task_struct *copy_process( if (retval) goto bad_fork_cancel_cgroup; =20 + /* + * Allocate a default futex hash for the user process once the first + * thread spawns. + */ + if (need_futex_hash_allocate_default(clone_flags)) { + retval =3D futex_hash_allocate_default(); + if (retval) + goto bad_fork_core_free; + /* + * If we fail beyond this point we don't free the allocated + * futex hash map. We assume that another thread will created + * and makes use of it The hash map will be freed once the main + * thread terminates. + */ + } /* * From this point on we must avoid any synchronous user-space * communication until we take the tasklist-lock. In particular, we do --=20 2.45.2