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Tue, 17 Mar 2026 16:19:12 +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 8njFLgB/uWkddQAAD6G6ig (envelope-from ); Tue, 17 Mar 2026 16:19:12 +0000 Date: Tue, 17 Mar 2026 16:19:11 +0000 From: Pedro Falcato To: Benjamin Eikel Cc: linux-mm@kvack.org, rcu@vger.kernel.org, Andrew Morton , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , David Hildenbrand Subject: Re: [BUG] RCU stall in unmap_page_range during exit_mmap (6.19 regression) Message-ID: <6ccygsneky6la4unzj2qd6m6o3ty3ek6xwidznzgrpdvc7tfel@qeoj7rramrmu> References: <6261958.lOV4Wx5bFT@thinkpad-benjamin> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6261958.lOV4Wx5bFT@thinkpad-benjamin> X-Spamd-Result: default: False [-3.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo] X-Spam-Flag: NO X-Spam-Score: -3.80 X-Spam-Level: +Cc a bunch of relevant people On Mon, Mar 16, 2026 at 09:18:37AM +0100, Benjamin Eikel wrote: > Dear Linux kernel developers, > > I have reported this issue as Debian bug #1130138 [1], which has been marked > “upstream”. I am therefore also reaching out here to make you aware of it. > Please let me know if you need additional information. > > After upgrading from linux-image-6.18.15+deb14-amd64, I see this error several > times and the system shortly freezes. It seems related to Zoom crashing first, > but the freezes were not noticable with older Linux kernels. Do you have a simpler repro you can share? > Currently booted into 6.18.15+deb14-amd64 which does not exhibit this issue. > The stalls occurred when running 6.19.6+deb14-amd64. More information about my > system can be found in the Debian bug report. > Can you attach the debian kernel config? Is it possible something relevant changed since 6.18? > Mär 09 09:13:48 thinkpad-benjamin kernel: rcu: INFO: rcu_preempt detected > stalls on CPUs/tasks: > Mär 09 09:13:48 thinkpad-benjamin kernel: rcu: Tasks blocked on > level-0 rcu_node (CPUs 0-15): P10008/1:b..l > Mär 09 09:13:48 thinkpad-benjamin kernel: rcu: (detected by 5, t=5252 > jiffies, g=177537, q=28067 ncpus=16) > Mär 09 09:13:48 thinkpad-benjamin kernel: task:zoom state:R > running task stack:0 pid:10008 tgid:10008 ppid:2089 > task_flags:0x40040c flags:0x00080802 > Mär 09 09:13:48 thinkpad-benjamin kernel: Call Trace: > Mär 09 09:13:48 thinkpad-benjamin kernel: > Mär 09 09:13:48 thinkpad-benjamin kernel: __schedule+0x48a/0xfc0 > Mär 09 09:13:48 thinkpad-benjamin kernel: preempt_schedule+0x32/0x50 > Mär 09 09:13:48 thinkpad-benjamin kernel: preempt_schedule_thunk+0x16/0x30 > Mär 09 09:13:48 thinkpad-benjamin kernel: _raw_spin_unlock+0x22/0x30 > Mär 09 09:13:48 thinkpad-benjamin kernel: unmap_page_range+0xbcb/0x1700 Hmm. We have a bunch of cond_resched() sprayed around this code. This _should_ work. I don't see anything particularly interesting that changed between 6.18 and 6.19. > Mär 09 09:13:48 thinkpad-benjamin kernel: unmap_vmas+0xa1/0x180 > Mär 09 09:13:48 thinkpad-benjamin kernel: exit_mmap+0xe1/0x3b0 > Mär 09 09:13:48 thinkpad-benjamin kernel: __mmput+0x41/0x150 > Mär 09 09:13:48 thinkpad-benjamin kernel: do_exit+0x251/0xa70 > Mär 09 09:13:48 thinkpad-benjamin kernel: do_group_exit+0x2d/0xc0 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:13:48 thinkpad-benjamin kernel: get_signal+0x8a4/0x920 > Mär 09 09:13:48 thinkpad-benjamin kernel: > arch_do_signal_or_restart+0x40/0x250 > Mär 09 09:13:48 thinkpad-benjamin kernel: exit_to_user_mode_loop+0x8e/0x480 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? __x64_sys_sched_setaffinity+0x6a/ > 0xb0 > Mär 09 09:13:48 thinkpad-benjamin kernel: do_syscall_64+0x20b/0x600 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? ksys_read+0xcd/0xf0 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? do_syscall_64+0xbe/0x600 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? do_syscall_64+0xbe/0x600 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? __x64_sys_close+0x3d/0x80 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? do_syscall_64+0xbe/0x600 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:13:48 thinkpad-benjamin kernel: ? exc_page_fault+0x7e/0x1a0 > Mär 09 09:13:48 thinkpad-benjamin kernel: > entry_SYSCALL_64_after_hwframe+0x76/0x7e > Mär 09 09:13:48 thinkpad-benjamin kernel: RIP: 0033:0x7f2876359e2d > Mär 09 09:13:48 thinkpad-benjamin kernel: RSP: 002b:00007ffc91243ad8 EFLAGS: > 00000246 ORIG_RAX: 00000000000000cb > Mär 09 09:13:48 thinkpad-benjamin kernel: RAX: 0000000000000000 RBX: > 00007f2875207700 RCX: 00007f2876359e2d > Mär 09 09:13:48 thinkpad-benjamin kernel: RDX: 00007ffc91243ae0 RSI: > 0000000000000080 RDI: 0000000000002718 > Mär 09 09:13:48 thinkpad-benjamin kernel: RBP: 0000000000000020 R08: > 0000000000000001 R09: 00007f2875206de8 > Mär 09 09:13:48 thinkpad-benjamin kernel: R10: 0000000000000000 R11: > 0000000000000246 R12: 00007ffc91243ae0 > Mär 09 09:13:48 thinkpad-benjamin kernel: R13: 00007ffc91243c80 R14: > 0000000000000000 R15: 0000000000000020 > Mär 09 09:13:48 thinkpad-benjamin kernel: > Mär 09 09:13:48 thinkpad-benjamin kernel: rcu: INFO: rcu_preempt detected > expedited stalls on CPUs/tasks: { P10008 } 5361 jiffies s: 1609 root: 0x0/T > Mär 09 09:13:48 thinkpad-benjamin kernel: rcu: blocking rcu_node structures > (internal RCU debug): > > Another one: > > Mär 09 09:14:51 thinkpad-benjamin kernel: rcu: INFO: rcu_preempt detected > stalls on CPUs/tasks: > Mär 09 09:14:51 thinkpad-benjamin kernel: rcu: Tasks blocked on > level-0 rcu_node (CPUs 0-15): P10008/1:b..l > Mär 09 09:14:51 thinkpad-benjamin kernel: rcu: (detected by 5, t=21007 > jiffies, g=177537, q=87903 ncpus=16) > Mär 09 09:14:51 thinkpad-benjamin kernel: task:zoom state:R > running task stack:0 pid:10008 tgid:10008 ppid:2089 > task_flags:0x40040c flags:0x00080802 > Mär 09 09:14:51 thinkpad-benjamin kernel: Call Trace: > Mär 09 09:14:51 thinkpad-benjamin kernel: > Mär 09 09:14:51 thinkpad-benjamin kernel: __schedule+0x48a/0xfc0 > Mär 09 09:14:51 thinkpad-benjamin kernel: preempt_schedule+0x32/0x50 > Mär 09 09:14:51 thinkpad-benjamin kernel: preempt_schedule_thunk+0x16/0x30 > Mär 09 09:14:51 thinkpad-benjamin kernel: _raw_spin_unlock+0x22/0x30 > Mär 09 09:14:51 thinkpad-benjamin kernel: unmap_page_range+0xbcb/0x1700 > Mär 09 09:14:51 thinkpad-benjamin kernel: unmap_vmas+0xa1/0x180 > Mär 09 09:14:51 thinkpad-benjamin kernel: exit_mmap+0xe1/0x3b0 > Mär 09 09:14:51 thinkpad-benjamin kernel: __mmput+0x41/0x150 > Mär 09 09:14:51 thinkpad-benjamin kernel: do_exit+0x251/0xa70 > Mär 09 09:14:51 thinkpad-benjamin kernel: do_group_exit+0x2d/0xc0 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:14:51 thinkpad-benjamin kernel: get_signal+0x8a4/0x920 > Mär 09 09:14:51 thinkpad-benjamin kernel: > arch_do_signal_or_restart+0x40/0x250 > Mär 09 09:14:51 thinkpad-benjamin kernel: exit_to_user_mode_loop+0x8e/0x480 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? __x64_sys_sched_setaffinity+0x6a/ > 0xb0 > Mär 09 09:14:51 thinkpad-benjamin kernel: do_syscall_64+0x20b/0x600 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? ksys_read+0xcd/0xf0 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? do_syscall_64+0xbe/0x600 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? do_syscall_64+0xbe/0x600 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? __x64_sys_close+0x3d/0x80 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? do_syscall_64+0xbe/0x600 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? > srso_alias_return_thunk+0x5/0xfbef5 > Mär 09 09:14:51 thinkpad-benjamin kernel: ? exc_page_fault+0x7e/0x1a0 > Mär 09 09:14:51 thinkpad-benjamin kernel: > entry_SYSCALL_64_after_hwframe+0x76/0x7e > Mär 09 09:14:51 thinkpad-benjamin kernel: RIP: 0033:0x7f2876359e2d > Mär 09 09:14:51 thinkpad-benjamin kernel: RSP: 002b:00007ffc91243ad8 EFLAGS: > 00000246 ORIG_RAX: 00000000000000cb > Mär 09 09:14:51 thinkpad-benjamin kernel: RAX: 0000000000000000 RBX: > 00007f2875207700 RCX: 00007f2876359e2d > Mär 09 09:14:51 thinkpad-benjamin kernel: RDX: 00007ffc91243ae0 RSI: > 0000000000000080 RDI: 0000000000002718 > Mär 09 09:14:51 thinkpad-benjamin kernel: RBP: 0000000000000020 R08: > 0000000000000001 R09: 00007f2875206de8 > Mär 09 09:14:51 thinkpad-benjamin kernel: R10: 0000000000000000 R11: > 0000000000000246 R12: 00007ffc91243ae0 > Mär 09 09:14:51 thinkpad-benjamin kernel: R13: 00007ffc91243c80 R14: > 0000000000000000 R15: 0000000000000020 > Mär 09 09:14:51 thinkpad-benjamin kernel: > Mär 09 09:14:52 thinkpad-benjamin kernel: rcu: INFO: rcu_preempt detected > expedited stalls on CPUs/tasks: { P10008 } 21233 jiffies s: 1609 root: 0x0/T > Mär 09 09:14:52 thinkpad-benjamin kernel: rcu: blocking rcu_node structures > (internal RCU debug): > > Note the stall duration escalating from t=5252 jiffies (~5s) to t=21007 jiffies > (~21s), with the same grace period (g=177537), indicating the unmap_page_range > operation blocked for over a minute. > > Kind regards > Benjamin > > [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1130138 > > > -- Pedro