From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D86E872604; Tue, 4 Nov 2025 23:05:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762297554; cv=none; b=cm0hFWMnuJgZSysxbDoT4cYt7NMyG5NuTWuqKnXJ4WQK5xI+QbQjq83N7oDl686ASJsHK2uUjWgAurZU42xO7EIMXA8uEQqeCPF1XQ9lRjoIpJUDnaF4TcvXwSKyjd5GGtjaTLnn2GupJfdah7CN5H2Wtw90T8CT/nicpxJLhg0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762297554; c=relaxed/simple; bh=WCtPTfqQtVxV9hfqYB2PSFajh5C8vxNraqseQ7UsQT8=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=qs3bl+nMGKajf1ihjfb1c8U04VYfZgCAoNE5XLuyZnVKOkoHjYwOZvO/KFyWEUdSIyHaOpgtX8W6wMy3Y8h9NUL06zH6GNlp+CG5aM9lrlAJZs9MFP5WlEYbeqNpAv7Mc2U1W2mVixd2I3WQXa8jZJFvPCPO1Cko/1NgLKMTPEU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BvFrfYpK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BvFrfYpK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82776C116D0; Tue, 4 Nov 2025 23:05:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762297554; bh=WCtPTfqQtVxV9hfqYB2PSFajh5C8vxNraqseQ7UsQT8=; h=From:Date:Subject:To:Cc:From; b=BvFrfYpKupJEmVnXZbkqAK4A4TwNe6EgVFqvWg7p+c+vnkMbi1H7+1HD9uz3JMxgd 1lS7/PcHA+LXoZuDCcJqkS8uoP1QOJrYjSt+CEJHUUBxI2eBTobtdFysyclroiVaAJ 4TZyoBpdVxeisLjyFkhPVnXp8FUmu5u415JLguayLOtao4qP+wDX5DixAIrObW9/xR vKLpdlZhLQzkgfF1IC9wIzBpqVLpZESLX9C7SgQgSlw4q70eEWQxJTuSf2cfFExaJe LTXd4OBi/uHg1yBl6cDrjrKMt0lZ8lHA+q+95FymfERSfQHasz/rP3sAHXCZKFCurr R+KW8ja0KDbyg== From: Christian Brauner Date: Wed, 05 Nov 2025 00:05:01 +0100 Subject: [PATCH] pidfs: reduce wait_pidfd lock scope Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251105-work-pidfs-wait_pidfd-lock-v1-1-02638783be07@kernel.org> X-B4-Tracking: v=1; b=H4sIAJyGCmkC/yXM0QqDMAyF4VeRXC+jVYSxVxljpG2qwdFKM3Qgv vvqvDsfB/4NlIuwwr3ZoPAiKjlV2EsDfqQ0MEqohta0vbWmxzWXCWcJUXEl+byOGfCd/YRknQn dzUfbBaiBuXCU7z/+eFY7UkZXKPnxSC5Rr+e/7z9kNtZ8iAAAAA== X-Change-ID: 20251105-work-pidfs-wait_pidfd-lock-a1b0d38cf13d To: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Christian Brauner X-Mailer: b4 0.15-dev-a6db3 X-Developer-Signature: v=1; a=openpgp-sha256; l=1448; i=brauner@kernel.org; h=from:subject:message-id; bh=WCtPTfqQtVxV9hfqYB2PSFajh5C8vxNraqseQ7UsQT8=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWRytV18kWbS+F/8n7clwz3W6K832YTTI3XeuefwRTjuK U0/bfa5o5SFQYyLQVZMkcWh3SRcbjlPxWajTA2YOaxMIEMYuDgFYCIylxkZ3kq/LFdLWt/Ee+r6 hO97f9xIXLgk0u+LSsrNzwqXag5yOTIy3HQSmJUazlNn8TXa+Odb/81e87e+/sbDuNArJnHJnDk F3AA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 There's no need to hold the lock after we realized that pid->attr is set. We're holding a reference to struct pid so it won't go away and pidfs_exit() is called once per struct pid. Signed-off-by: Christian Brauner --- fs/pidfs.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/fs/pidfs.c b/fs/pidfs.c index 0ef5b47d796a..d2e74c069b4f 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -613,17 +613,19 @@ void pidfs_exit(struct task_struct *tsk) might_sleep(); - guard(spinlock_irq)(&pid->wait_pidfd.lock); - attr = pid->attr; - if (!attr) { - /* - * No one ever held a pidfd for this struct pid. - * Mark it as dead so no one can add a pidfs - * entry anymore. We're about to be reaped and - * so no exit information would be available. - */ - pid->attr = PIDFS_PID_DEAD; - return; + /* Synchronize with pidfs_register_pid(). */ + scoped_guard(spinlock_irq, &pid->wait_pidfd.lock) { + attr = pid->attr; + if (!attr) { + /* + * No one ever held a pidfd for this struct pid. + * Mark it as dead so no one can add a pidfs + * entry anymore. We're about to be reaped and + * so no exit information would be available. + */ + pid->attr = PIDFS_PID_DEAD; + return; + } } /* --- base-commit: a20432b6571ddc02e86c549f582d61ac5a89ca40 change-id: 20251105-work-pidfs-wait_pidfd-lock-a1b0d38cf13d