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Sat, 13 Sep 2025 20:46:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id KfLDIjbYxWjcZAAAD6G6ig (envelope-from ); Sat, 13 Sep 2025 20:46:46 +0000 Message-ID: Date: Sat, 13 Sep 2025 22:46:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [vbabka-slab:slab/for-6.18/kmalloc_nolock 14/14] mm/slub.c:3866:2: warning: variable 'flags' is used uninitialized whenever '&&' condition is false Content-Language: en-US To: Alexei Starovoitov Cc: kernel test robot , Alexei Starovoitov , Harry Yoo , clang-built-linux , oe-kbuild-all@lists.linux.dev, linux-mm References: <202509121822.aOV6H1ts-lkp@intel.com> <8fe99133-3322-4e39-9b58-80df547b8d1f@suse.cz> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: C199F80004 X-Stat-Signature: f8pjtzx7fnbharcmb993i5o4d633pgta X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1757796408-944661 X-HE-Meta: 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 GDIVw4Uo G4zWXziMnn1d3qpuM2NhuwAZPiqA5+vcO+UOEV0RnWhrShAZpiO0xVfOHpxFsD7r+V+7x33f1vyodNGbhmw/1IgxW5xlhVlBCfOpFRSpY392FNNyNkVIt94BIRWuLaXDT3wImNbT4vdSVgeosiHIil1OJux4ZhNAJ+voRmh4RjPXTlxFNFwT95twEfHga1DSJI8o1YJVT4XIPyBBB2AL9d7OC2/zCyTTrO4+QVM+hmkhXeSIfISiq77gq25LoVT22xiSu9clWmEktlqu6rpslHSW6c7Se4Mc2IWRGPi3VVWb2x6ayf1AvBJvzMMohCUR7rau8J8ztlfGY7prfOWrhqwNGpmcTWnqzzoi0fOl/7Q0HMPh4DIkPpjoQ4G3bF/QcxiPoHSqvIQ48zT4b6QestiHZOpBQ8ZfXkaOLvOcjmJhnKhZyyB6URm/aQDO6Ksy/MW+JFF+sv9DR2MQQLiq+17iWog== 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 9/12/25 18:39, Alexei Starovoitov wrote: > On Fri, Sep 12, 2025 at 6:23 AM Vlastimil Babka wrote: >> >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -3772,8 +3772,11 @@ static void deactivate_slab(struct kmem_cache *s, struct slab *slab, >> #define local_lock_cpu_slab(s, flags) \ >> local_lock_irqsave(&(s)->cpu_slab->lock, flags) >> #else >> -#define local_lock_cpu_slab(s, flags) \ >> - lockdep_assert(local_trylock_irqsave(&(s)->cpu_slab->lock, flags)) >> +#define gg(s, flags) \ >> + do { \ >> + bool __l = local_trylock_irqsave(&(s)->cpu_slab->lock, flags); \ >> + lockdep_assert(__l); > > That works, but would raise questions for anyone looking at > these two lines as-is, since it's an implementation > detail of lockdep_assert() and combination of .config flags. TBH when I see some code with a side-effect wrapped in a WARN or assert that can be configured off, it already raises a question if that gets executed when configured off. There are examples where it does, and where it doesn't. > what clang warning suggested is imo cleaner: That silences the warning about flags, however it means that when lockdep gets disabled on runtime, the locks stop locking (but not unlocking). While debug_locks_off() only seems to get called in a serious situations currently, we should not make things even worse then. > diff --git a/mm/slub.c b/mm/slub.c > index 4079abb5d0e1..a6b50cd1d95f 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3865,7 +3865,7 @@ static void put_cpu_partial(struct kmem_cache > *s, struct slab *slab, int drain) > { > struct slab *oldslab; > struct slab *slab_to_put = NULL; > - unsigned long flags; > + unsigned long flags = 0; > int slabs = 0; > > Could you fold one of them in? And so I've folded in mine.