From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?UTF-8?q?Michal=20Koutn=C3=BD?= <mkoutny@suse.com>
Subject: [RFC PATCH 3/3] cgroup: Do not take css_set_lock in cgroup_show_path
Date: Tue,  2 May 2023 15:38:47 +0200
Message-ID: <20230502133847.14570-4-mkoutny@suse.com>
References: <20230502133847.14570-1-mkoutny@suse.com>
Mime-Version: 1.0
Content-Transfer-Encoding: base64
Return-path: <linux-fsdevel-owner@vger.kernel.org>
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1;
        t=1683034730; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc:
         mime-version:mime-version:content-type:content-type:
         content-transfer-encoding:content-transfer-encoding:
         in-reply-to:in-reply-to:references:references;
        bh=fpw1/CS8jewUjSsdmSx7N0a/briOC9eP8uaWobg+SbE=;
        b=fE3Cff0u2uDDZoTwPGZOiCHhWMWW2sCmMD5CFUkuzcVoLi2vh0pm8Rwr/uTuKzp8yUeamE
        ny+LtbLzNp+7qONlp+LrgnBakxzmXydMKFc3U8iqdaukFUOm4Q7DmwqXXxGO0WxmdDOEX8
        ka0xGI08HvsuJRFVAK3WDLeiAiUHjZA=
In-Reply-To: <20230502133847.14570-1-mkoutny@suse.com>
List-ID: <cgroups.vger.kernel.org>
Content-Type: text/plain; charset="macroman"
To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org
Cc: Alexander Viro <viro@zeniv.linux.org.uk>, Christian Brauner <brauner@kernel.org>, Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>, Johannes Weiner <hannes@cmpxchg.org>, Dave Chinner <dchinner@redhat.com>, Rik van Riel <riel@surriel.com>, Jiri Wiesner <jwiesner@suse.de>
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