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Mon, 29 Jun 2026 05:47:08 -0700 (PDT) Date: Mon, 29 Jun 2026 14:47:05 +0200 From: Petr Mladek To: sanan.hasanou@gmail.com Cc: rostedt@goodmis.org, john.ogness@linutronix.de, senozhatsky@chromium.org, linux-kernel@vger.kernel.org, syzkaller@googlegroups.com, contact@pgazz.com Subject: Re: BUG: soft lockup in kernel_init Message-ID: References: <6a3eee90.4ad61264.123291.5a4c@mx.google.com> 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-Disposition: inline In-Reply-To: <6a3eee90.4ad61264.123291.5a4c@mx.google.com> On Fri 2026-06-26 14:26:40, sanan.hasanou@gmail.com wrote: > Good day, dear maintainers, > > We found a bug using a modified version of syzkaller. > > Kernel Branch: 7.0-rc1 > Kernel Config: > Unfortunately, we don't have any reproducer for this bug yet. > Thank you! > > Best regards, > Sanan Hasanov > > watchdog: BUG: soft lockup - CPU#0 stuck for 142s! [swapper/0:1] > Modules linked in: > irq event stamp: 1640392 > hardirqs last enabled at (1640391): [] console_trylock_spinning kernel/printk/printk.c:2032 [inline] > hardirqs last enabled at (1640391): [] vprintk_emit+0x3b3/0x550 kernel/printk/printk.c:2478 > hardirqs last disabled at (1640392): [] sysvec_apic_timer_interrupt+0xe/0xb0 arch/x86/kernel/apic/apic.c:1056 > softirqs last enabled at (1640360): [] __do_softirq kernel/softirq.c:656 [inline] > softirqs last enabled at (1640360): [] invoke_softirq kernel/softirq.c:496 [inline] > softirqs last enabled at (1640360): [] __irq_exit_rcu+0x60/0x150 kernel/softirq.c:723 > softirqs last disabled at (1640327): [] __do_softirq kernel/softirq.c:656 [inline] > softirqs last disabled at (1640327): [] invoke_softirq kernel/softirq.c:496 [inline] > softirqs last disabled at (1640327): [] __irq_exit_rcu+0x60/0x150 kernel/softirq.c:723 > CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0-rc1 #1 PREEMPT(full) > Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > RIP: 0010:console_trylock_spinning kernel/printk/printk.c:2039 [inline] This code is from kernel/printk/printk.c (7.0-rc1): 1080 static int console_trylock_spinning(void) 1081 { [...] 2025 /* We spin waiting for the owner to release us */ 2026 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); 2027 /* Owner will clear console_waiter on hand off */ 2028 while (READ_ONCE(console_waiter)) 2029 cpu_relax(); 2030 spin_release(&console_owner_dep_map, _THIS_IP_); 2031 2032 printk_safe_exit_irqrestore(flags); 2033 /* 2034 * The owner passed the console lock to us. 2035 * Since we did not spin on console lock, annotate 2036 * this as a trylock. Otherwise lockdep will 2037 * complain. 2038 */ 2039 mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_); The softlockup has been reported right after console_trylock_spinning() has got the ownership and enabled interrupts again. It allowed to process timers, including the watchdog_timer_fn(). It means that console_trylock_spinning() has been called in task context, the interrupts were disabled inside this function and it has been busy waiting for a long time (~140s). The shows that the caller has been blocked. Unfortunately, the log does not show who blocked it. Some hint might give a full log with with timestamps. Could you please provide it, please? Best Regards, Petr > RIP: 0010:vprintk_emit+0x453/0x550 kernel/printk/printk.c:2478 > Code: 0f 84 44 ff ff ff e8 5c d7 1f 00 fb eb 44 e8 54 d7 1f 00 e8 af 78 b5 09 4d 85 f6 74 94 e8 45 d7 1f 00 fb 48 c7 c7 20 e0 d4 8d <31> f6 ba 01 00 00 00 31 c9 41 b8 01 00 00 00 45 31 c9 53 e8 a5 35 > RSP: 0018:ffffc9000012f220 EFLAGS: 00000293 > RAX: ffffffff819f610b RBX: ffffffff819f5f85 RCX: ffff88801a6f5700 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8dd4e020 > RBP: ffffc9000012f2d0 R08: ffffffff8f722db7 R09: 1ffffffff1ee45b6 > R10: dffffc0000000000 R11: fffffbfff1ee45b7 R12: 0000000000000045 > R13: 0000000000000000 R14: 0000000000000200 R15: 0000000000000000 > FS: 0000000000000000(0000) GS:ffff88809ab94000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffff8880186b4000 CR3: 000000000db4a000 CR4: 00000000000006f0 > Call Trace: > > dev_vprintk_emit+0x337/0x3f0 drivers/base/core.c:4913 > dev_printk_emit+0xe0/0x120 drivers/base/core.c:4924 > _dev_info+0x10a/0x150 drivers/base/core.c:4982 > cmos_do_probe+0xca4/0x1020 drivers/rtc/rtc-cmos.c:1121 > pnp_device_probe+0x305/0x4b0 drivers/pnp/driver.c:111 > call_driver_probe drivers/base/dd.c:-1 [inline] > really_probe+0x258/0xae0 drivers/base/dd.c:661 > __driver_probe_device+0x18c/0x320 drivers/base/dd.c:803 > driver_probe_device+0x4f/0x230 drivers/base/dd.c:833 > __driver_attach+0x3e1/0x710 drivers/base/dd.c:1227 > bus_for_each_dev+0x22c/0x2a0 drivers/base/bus.c:383 > bus_add_driver+0x340/0x670 drivers/base/bus.c:715 > driver_register+0x23a/0x310 drivers/base/driver.c:249 > cmos_init+0x11/0x80 drivers/rtc/rtc-cmos.c:1546 > do_one_initcall+0x1eb/0x870 init/main.c:1382 > do_initcall_level+0x104/0x190 init/main.c:1444 > do_initcalls+0x59/0xa0 init/main.c:1460 > kernel_init_freeable+0x2a0/0x3e0 init/main.c:1692 > kernel_init+0x1d/0x1c0 init/main.c:1582 > ret_from_fork+0x507/0xb90 arch/x86/kernel/process.c:158 > ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:245 > > > <<<<<<<<<<<<<<< tail report >>>>>>>>>>>>>>>