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Mon, 12 Jan 2026 06:50:56 -0800 (PST) MIME-Version: 1.0 References: <6964f35e.050a0220.eaf7.00a5.GAE@google.com> <20260112133815.2190-1-hdanton@sina.com> In-Reply-To: <20260112133815.2190-1-hdanton@sina.com> From: Deepanshu Kartikey Date: Mon, 12 Jan 2026 20:20:45 +0530 X-Gm-Features: AZwV_QjARb9LLRGnT6VuwKGPoAGdxehdX8bvZUqlvSs_RWCwUZR0FmWi_jJLjDQ Message-ID: Subject: Re: [syzbot] [mm?] INFO: rcu detected stall in purge_vmap_node To: Hillf Danton Cc: syzbot , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, urezki@gmail.com Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: 1z3ub45ksq3b1mtt6n5zgonzsks6j3ac X-Rspamd-Queue-Id: 185DCC000F X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1768229457-46352 X-HE-Meta: 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 Bs21Mv5e 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 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 Mon, Jan 13, 2026 at 07:08:XX, Hillf Danton wrote: > Given the test result of your patch, can you specify the root cause > of the stall reported, Deepanshu? Hi Hillf, Thank you for the question. Looking at the stall in the test log, this is occurring in a different code path from what my patch addresses: My patch fixes: kasan_release_vmalloc_node+0x1ba/0xad0 mm/vmalloc.c:2299 purge_vmap_node+0x1ba/0xad0 New stall location: __reset_page_owner+0x84/0x1a0 __free_frozen_pages+0x7df/0x1170 vfree+0x1fd/0xb50 cleanup_vm_area_work+0x4c/0x100 The root cause pattern is similar (CONFIG_PAGE_OWNER stack unwinding under RCU read lock), but manifesting in the page freeing path rather than the KASAN shadow cleanup path. My patch specifically addresses the unbounded loop in kasan_release_vmalloc_node() where we iterate through large purge_lists. The new stall appears to be in __reset_page_owner() during page freeing, which would need a separate fix in that code path. Should I focus on submitting v2 of my vmalloc fix, or would you prefer I investigate the page_owner stall as well? Best regards, Deepanshu