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b=GDJCvsb59yNSCzj2fnsZ7US1xTmRV/TBed8SYWPpTWVcGQ2xxUj1YnDNzXxzPG8Z4 JTeqhvVnUdcjyNaZieLaCr09B12zYUzam2xNWtM0ES//rovy0Vpl9gkb8HZW2HTK8K lu6HPajYMyVyXqrK1w6VPI3zJqRUEYG4/ZWalaStA1p+urtYyduQw9g6B5+3s/HoQz XFhs1I8d+VI485wDpL0OLs0BT5JAwH/+z4s5Fj5/mc59cMJgqf/xxf1cfhGJ7FiGSh 1Ep2q2dttFz5a5M//OABnAcPG7F42bZKySMdudqlI1SgmPg+wEsmUlbgcQO0CVoBJE 5bKJ8klCoxhmA== From: Pratyush Yadav To: Pasha Tatashin Cc: rppt@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, dmatlack@google.com, pratyush@kernel.org, skhawaja@google.com Subject: Re: [PATCH v3 02/10] liveupdate: Synchronize lazy initialization of FLB private state In-Reply-To: <20260327033335.696621-3-pasha.tatashin@soleen.com> (Pasha Tatashin's message of "Fri, 27 Mar 2026 03:33:26 +0000") References: <20260327033335.696621-1-pasha.tatashin@soleen.com> <20260327033335.696621-3-pasha.tatashin@soleen.com> Date: Tue, 31 Mar 2026 10:38:12 +0000 Message-ID: <2vxzecl0i8rv.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: 9A035100004 X-Stat-Signature: r5zayr9n7jnduqda6mwmwf18zz6ci7a8 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1774953497-440196 X-HE-Meta: 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 8YHdvqaM VAW03OhxDAh0+r9gzrr+rtDxfjIq13VEjMionLV0gdngbwu+N3QRh36/5bfAJEKaNo1JYKt1jiIaCf/4LPRz5lNsBoUswyVGQuMzPolpKemSUNfmbzGr8RJ5alfPVvZFE4BSK7NRbNAy13px6ncYkBMD0VVTZPvX+/VfaAYL0MdltzXBzgQeC9DWJEXv4stit/RJVa8LH0QMtzZCdzDxO2V6M92eBmdxxzI3NkxsVN1AloPHkiqtaEYMFLxszIgScWx1m Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Mar 27 2026, Pasha Tatashin wrote: > The luo_flb_get_private() function, which is responsible for lazily > initializing the private state of FLB objects, can be called > concurrently from multiple threads. This creates a data > race on the 'initialized' flag and can lead to multiple executions of > mutex_init() and INIT_LIST_HEAD() on the same memory. > > Introduce a static spinlock (luo_flb_init_lock) local to the function > to synchronize the initialization path. Use smp_load_acquire() and > smp_store_release() for memory ordering between the fast path and the > slow path. > > Signed-off-by: Pasha Tatashin Reviewed-by: Pratyush Yadav But... wouldn't it be a whole lot simpler if we introduce a DEFINE_LUO_FLB() and get rid of luo_flb_get_private() entirely: #define DEFINE_LUO_FLB(_name, _ops, _compatible) \ struct liveupdate_flb _name = { \ .ops = _ops, \ .compatible = _compatible, \ .private = { \ .list = LIST_HEAD_INIT(_name.private.list), \ .list = LIST_HEAD_INIT(_name.private.list), \ / ... }, \ } I can't get sparse to work so not sure if I need some special syntax to initialize stuff in .private, but I reckon we can get something working. [...] -- Regards, Pratyush Yadav