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bh=JpRyuuJJeXMepCuk4dxVJkRfLtOIeOpXAxCVzCQEjRo=; b=V3ENFQBGOdFQEaBx8Zl/xtMFcug3VA8Hc66H4GDlrAWGh9SLu1eMKzb+/avBgI2pzB0Erc 9ogjb2lJrvyDSsC3Qr5znDmfNNYG+1Vuiu1JuC3O/FoNG+aqnYZFlfE/FxjWAaUY+93pzW Ou6zF1VBQEU7RnpQ89rQuUzp02EXNHiUQFoBr9410wK2cu3xZIH7jA9i0enxRXkKYjyy46 Lo6JOWOxkH9KUChbf3p7jce8aKPagO4Rj4abKynFXKNoJKhftL4UPU7T7JGvw+I4jNJoSD F5b7f3hSap9XTZ+KcVrmndko5hzPdqWpEf2Ul5N+uBCJBP2NA5p7lYGm13ekfg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1716532988; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=JpRyuuJJeXMepCuk4dxVJkRfLtOIeOpXAxCVzCQEjRo=; b=79zbjKzijYSkmmeKFFiga6ihntljixAbKVzEYcXHAgJQcL50JnXhzAUvWfOyZAGb6zz7Oc rmes18ee96w6L5Ag== From: Sebastian Andrzej Siewior To: Vlastimil Babka Cc: Thomas Gleixner , syzbot , bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, linux-kernel@vger.kernel.org, mingo@redhat.com, syzkaller-bugs@googlegroups.com, x86@kernel.org, linux-mm@kvack.org, Tejun Heo , Lai Jiangshan Subject: Re: [syzbot] [kernel?] WARNING in flush_cpu_slab Message-ID: <20240524064306.b98TP1nU@linutronix.de> References: <0000000000008c9d27061915ca9c@google.com> <87v834g6hn.ffs@tglx> <2149ee23-5321-4422-808f-e6a9046662fc@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2149ee23-5321-4422-808f-e6a9046662fc@suse.cz> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 3685A140016 X-Stat-Signature: jzcrjzgdkzxhkwhxjfphspcfhq5xe1m4 X-HE-Tag: 1716532990-587686 X-HE-Meta: U2FsdGVkX18zmIjLlijSppvz9tgaVvdrsTr4i+4xZWAlbmRV6JAV85Sjl+6IGTR0JExg2d9jfENEldmsWvnTA0WdWYjldZJI5PMuoUSO4CUJ33RfYb6VE+MAmOso1B9R4NyvN50PZktyGwBYJfyaKhjx0eSs5jUtNtTL6u90NcIgRa1BykC1CofUYWxlPwMsTfD5Ns4P5RhI7PAF8GmA4EFtHdtFPoaB9eqsP4TJ77XvMJlpC4SYR/FTobNRerEBVqkyxvK7I0VqMgOccMtXm0147WvTmTaCInbwPC98E6dxMB/56+kUjQvH7SY2kFVOZZCcr3C384TmJkhpdN0rwKYTTnN1eVulWbd1lKJZpAQNOwwy9B0JnbmtneqEjrskUC/IrykEFdrsZnUf4/V/ao4R/SwhOntIuu+6Bhm+jMeE7Vjam3KxBIwCNgwT9VOg3ZoJbxhyqjbpw+mZPO11p2RMgf47QSgAe2MHa8o80yQLgf7vyKq/hzB6ZOA2vO7+dkpFAM7+0yf2uxNSAgoum1gVk6pmw4sX03bnPxnKNnAPz9RTWOQR5czPIf4RV5ytq2hgGA0xyljHmnNDKPvWVLqQLm7n5VrCnk/xZds+XlS3coA4iRohAZM9LUhaG431hovgRTOrlDrHEpNebMHm2yxQ8z7bMQgsozABnae6VhF1VspcrYyG/af7i13deqRYUqu584nbYfh2mQx8N7whNcQZTDuGzZOVgDMbVl2aKBA44XKG+FBa9mpvA7tHRLteU+gj6i+fmnfm0dRD5xmITQS+IgZdotwVLBiHJu7X8uoDu5mqhEDvFXSH72Mq1ahH1VAiCinXIKAmpYM8vSsK+py9q9H0GK2WndDyz2AQpkkbg+1i6LF4hjP0dC+XFbZxvj/cgzSoFHU32gLQA3NouuY+UN7PNVKlUB7HzGs9s5IT5mFGyw4rz7QjEWL2h7ZAFZN88gEHEIKo0eIZhhj yuM0lEEe jSNA4D+Cte0oYcAukZF1g5gPCAFnOztwBSJNGiuzIgxJcG9tgl/oNRyZo0VbgljpBnMee9D2t9B+2Xam1V4QVJXtkzvb/EZ1C6e4LqcMgIC/x/QDo6HGT2lkCEw75E+ArRJz6ZE86SYzKvmHpomUJ3AMFSaptFhvfP3EWYjzGCLLJcNin7KVQBIUioNvMmNffiV8aN2/cCwp+dJw7r7tEYOPzNM7RiZRnyvl4qxDL0L60t5bDDDhsj2kuPqP46sZMFgwHmYz/j9mLjb1o6h1JEk6XJSSTeVEiMOH4 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 2024-05-23 23:03:52 [+0200], Vlastimil Babka wrote: > I'm puzzled by this. We use local_lock_irqsave() on !PREEMPT_RT everywhere. > IIUC this warning says we did the irqsave() and then found out somebody else > already set the owner? But that means they also did that irqsave() and set > themselves as l->owner. Does that mey there would be a spurious irq enable > that didn't go through local_unlock_irqrestore()? correct. > > Also this particular stack is from the work, which is scheduled by > queue_work_on() in flush_all_cpus_locked(), which also has a > lockdep_assert_cpus_held() so it should fullfill the "the caller must ensure > the cpu doesn't go away" property. But I think even if this ended up on the > wrong cpu (for the full duration or migrated while processing the work item) > somehow, it wouldn't be able to cause such warning, but rather corrupt > something else Based on > >> CPU: 3 PID: 5221 Comm: kworker/3:3 Not tainted 6.9.0-syzkaller-10713-g2a8120d7b482 #0 the code was invoked on CPU3 and the kworker was made for CPU3. This is all fine. All access for the lock in question is within a few lines so there is no unbalance lock/ unlock or IRQ-unlock which could explain it. Sebastian