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Howlett" , Suren Baghdasaryan , Alexei Starovoitov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, bpf@vger.kernel.org, kasan-dev@googlegroups.com, "Paul E. McKenney" Subject: Re: [PATCH v4 02/22] mm/slab: fix false lockdep warning in __kfree_rcu_sheaf() Message-ID: <20260123120302.TsiVMAQb@linutronix.de> References: <20260123-sheaves-for-all-v4-0-041323d506f7@suse.cz> <20260123-sheaves-for-all-v4-2-041323d506f7@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20260123-sheaves-for-all-v4-2-041323d506f7@suse.cz> X-Stat-Signature: tsu85ezurc55pyserezpcbdnca1t55dt X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 74444100014 X-HE-Tag: 1769169786-327971 X-HE-Meta: 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 6yj26EPh Kn4dZUA/SlJsv1PAZ7iRHvto+kfyknSndciAhEKY5oZja+KhGCa3kUeoZTNrf7JuooLbtwN83o9YMHe0PSJHeTEiAsT6/hdEaJBKEbuwhdSe7JGSh+eCy3SO/GCBIzQ0Eno+iI4ZxCRNlwSoAvJ15MRcDc/alhIC4x52TLpfVn+rRbOY4leCPK4IplB2vQAShshojxeAuVEADxhWc7YuvfdZ1bsHBZvhXJcQw6BVNDckv8yyTS4ose3IYCw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026-01-23 07:52:40 [+0100], Vlastimil Babka wrote: > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -6268,11 +6268,26 @@ static void rcu_free_sheaf(struct rcu_head *head) =E2=80=A6 > +static DEFINE_WAIT_OVERRIDE_MAP(kfree_rcu_sheaf_map, LD_WAIT_CONFIG); > + > bool __kfree_rcu_sheaf(struct kmem_cache *s, void *obj) > { > struct slub_percpu_sheaves *pcs; > struct slab_sheaf *rcu_sheaf; Would it work to have here something like BUG_ON(IS_ENABLED(CONFIG_PREEMPT_RT)); or WARN_ON+return? The way the code is now it relies on the check in kvfree_call_rcu() and tells lockdep to be quiet. And since it gets optimized away=E2=80=A6 > + lock_map_acquire_try(&kfree_rcu_sheaf_map); > + Reviewed-by: Sebastian Andrzej Siewior Sebastian