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bh=9LjR+hMgOOIviyFlXVxnmansGbWA8tKdpCQ1OTyis+o=; b=uMfNdSWLan27BfBWRRXv+xSmDwICEfuBA3xX+rten5acv3HYwS3l2yJsq8RwiBlqhXCV6y FQoFWnfSfNsByYAA== From: Nam Cao To: Patrik Jakobsson Cc: Takashi Iwai , Harshit Mogalapalli , Helge Deller , Thomas Zimmermann , Daniel Vetter , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, bigeasy@linutronix.de, LKML , Vegard Nossum , George Kennedy , Darren Kenny , chuansheng.liu@intel.com Subject: Re: [bug-report] task info hung problem in fb_deferred_io_work() Message-ID: <20240419173443.6c49706e@namcao> In-Reply-To: References: <271372d6-e665-4e7f-b088-dee5f4ab341a@oracle.com> <20240418160652.68df1a86@namcao> <87ttjywxv5.wl-tiwai@suse.de> <878r19voks.wl-tiwai@suse.de> <5febb249-1d4d-4ea7-b031-1df4d14620d2@oracle.com> <8734rhvlr2.wl-tiwai@suse.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On 2024-04-19 Patrik Jakobsson wrote: > Neither cancel_delayed_work_sync() or flush_delayed_work() prevent new > work from being scheduled after they return. flush_delayed_work() is called during device closing. And because no writes are performed after the device has been closed, no new work should be queued after flush_delayed_work(). > But > cancel_delayed_work_sync() at least makes sure the queue is empty so > the problem becomes less apparent. > > Could this explain what we're seeing? I suspect that cancel_delayed_work_sync() is only treating the symptoms by preventing the deferred work from running. The real bug is "someone" giving fb_deferred_io_work() invalid pages to work with. But that's just a blind guess. Best regards, Nam