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Tue, 31 Mar 2026 00:42:03 -0700 (PDT) Date: Tue, 31 Mar 2026 00:42:03 -0700 In-Reply-To: <20260330175824.2777270-1-urezki@gmail.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69cb7acb.050a0220.183828.0025.GAE@google.com> Subject: [syzbot ci] Re: mm/vmalloc: Use dedicated unbound workqueue for vmap purge/drain From: syzbot ci To: akpm@linux-foundation.org, bhe@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lirongqing@baidu.com, urezki@gmail.com Cc: syzbot@lists.linux.dev, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot ci has tested the following series [v2] mm/vmalloc: Use dedicated unbound workqueue for vmap purge/drain https://lore.kernel.org/all/20260330175824.2777270-1-urezki@gmail.com * [PATCH v2] mm/vmalloc: Use dedicated unbound workqueue for vmap purge/drain and found the following issue: possible deadlock in touch_wq_lockdep_map Full report is available here: https://ci.syzbot.org/series/4a8f638e-3a3f-4346-8189-2b5a0eb9ceaf *** possible deadlock in touch_wq_lockdep_map tree: mm-new URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm.git base: af42d6d3650b95295a3f08fc35189998bc26c2e1 arch: amd64 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 config: https://ci.syzbot.org/builds/d94b1f61-6a69-4415-b385-b3c99018e8c2/config syz repro: https://ci.syzbot.org/findings/01e4d436-e924-4ce6-8902-78c6000bf34e/syz_repro ============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- kworker/u9:1/33 is trying to acquire lock: ffff88810168e948 ((wq_completion)vmap_drain){+.+.}-{0:0}, at: touch_wq_lockdep_map+0xb5/0x180 kernel/workqueue.c:3991 but task is already holding lock: ffff88810168e948 ((wq_completion)vmap_drain){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3251 [inline] ffff88810168e948 ((wq_completion)vmap_drain){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3359 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock((wq_completion)vmap_drain); lock((wq_completion)vmap_drain); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by kworker/u9:1/33: #0: ffff88810168e948 ((wq_completion)vmap_drain){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3251 [inline] #0: ffff88810168e948 ((wq_completion)vmap_drain){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3359 #1: ffffc90000a97c40 (drain_vmap_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3252 [inline] #1: ffffc90000a97c40 (drain_vmap_work){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3359 #2: ffffffff8e87ed68 (vmap_purge_lock){+.+.}-{4:4}, at: drain_vmap_area_work+0x17/0x40 mm/vmalloc.c:2443 #3: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline] #3: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline] #3: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: start_flush_work kernel/workqueue.c:4234 [inline] #3: ffffffff8e75e5e0 (rcu_read_lock){....}-{1:3}, at: __flush_work+0x100/0xc50 kernel/workqueue.c:4292 stack backtrace: CPU: 1 UID: 0 PID: 33 Comm: kworker/u9:1 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Workqueue: vmap_drain drain_vmap_area_work Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041 check_deadlock kernel/locking/lockdep.c:3093 [inline] validate_chain kernel/locking/lockdep.c:3895 [inline] __lock_acquire+0x253f/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:3991 start_flush_work kernel/workqueue.c:4272 [inline] __flush_work+0x87c/0xc50 kernel/workqueue.c:4292 __purge_vmap_area_lazy+0x7db/0xab0 mm/vmalloc.c:2419 drain_vmap_area_work+0x27/0x40 mm/vmalloc.c:2444 process_one_work kernel/workqueue.c:3276 [inline] process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 *** If these findings have caused you to resend the series or submit a separate fix, please add the following tag to your commit message: Tested-by: syzbot@syzkaller.appspotmail.com --- This report is generated by a bot. It may contain errors. syzbot ci engineers can be reached at syzkaller@googlegroups.com. To test a patch for this bug, please reply with `#syz test` (should be on a separate line). The patch should be attached to the email. Note: arguments like custom git repos and branches are not supported.