Thu, Mar 28, 2024 at 03:11:33PM +1100, Finn Thain kirjoitti: > The mitigation was intended to stop the irq completely. That might have > been better than a hard lock-up but it turns out that you get a crash > anyway if you're using pmac_zilog as a serial console. > > That's because the pr_err() call in pmz_receive_chars() results in > pmz_console_write() attempting to lock a spinlock already locked in > pmz_interrupt(). With CONFIG_DEBUG_SPINLOCK=y, this produces a fatal > BUG splat like the one below. (The spinlock at 0x62e140 is the one in > struct uart_port.) > > Even when it's not fatal, the serial port rx function ceases to work. > Also, the iteration limit doesn't play nicely with QEMU. Please see > bug report linked below. > > A web search for reports of the error message "pmz: rx irq flood" didn't > produce anything. So I don't think this code is needed any more. Remove it.
> [ 14.560000] ttyPZ0: pmz: rx irq flood ! > [ 14.560000] BUG: spinlock recursion on CPU#0, swapper/0 > [ 14.560000] lock: 0x62e140, .magic: dead4ead, .owner: swapper/0, > .owner_cpu: 0 > [ 14.560000] CPU: 0 PID: 0 Comm: swapper Not tainted > 6.8.0-mac-dbg-preempt-00004-g4143b7b9144a #1 > [ 14.560000] Stack from 0059bcc4: > [ 14.560000] 0059bcc4 0056316f 0056316f 00002700 004b6444 0059bce4 > 004ad8c6 0056316f > [ 14.560000] 0059bd10 004a6546 00556759 0062e140 dead4ead 0059f892 > 00000000 00000000 > [ 14.560000] 0062e140 0059bde8 005c03d0 0059bd24 0004daf6 0062e140 > 005567bf 0062e140 > [ 14.560000] 0059bd34 004b64c2 0062e140 00000001 0059bd50 002e15ea > 0062e140 00000001 > [ 14.560000] 0059bde7 0059bde8 005c03d0 0059bdac 0005124e 005c03d0 > 005cdc00 0000002b > [ 14.560000] 005a3caa 005a3caa 00000000 0059bde8 0004ff00 0059be8b > 00038200 000529ba > [ 14.560000] Call Trace: [<00002700>] ret_from_kernel_thread+0xc/0x14 > [ 14.560000] [<004b6444>] _raw_spin_lock+0x0/0x28 > [ 14.560000] [<004ad8c6>] dump_stack+0x10/0x16 > [ 14.560000] [<004a6546>] spin_dump+0x6e/0x7c > [ 14.560000] [<0004daf6>] do_raw_spin_lock+0x9c/0xa6 > [ 14.560000] [<004b64c2>] _raw_spin_lock_irqsave+0x2a/0x34 > [ 14.560000] [<002e15ea>] pmz_console_write+0x32/0x9a > [ 14.560000] [<0005124e>] console_flush_all+0x112/0x3a2 > [ 14.560000] [<0004ff00>] console_trylock+0x0/0x7a > [ 14.560000] [<00038200>] parameq+0x48/0x6e > [ 14.560000] [<000529ba>] __printk_safe_enter+0x0/0x36 > [ 14.560000] [<0005113c>] console_flush_all+0x0/0x3a2 > [ 14.560000] [<000542c4>] prb_read_valid+0x0/0x1a > [ 14.560000] [<004b65a4>] _raw_spin_unlock+0x0/0x38 > [ 14.560000] [<0005151e>] console_unlock+0x40/0xb8 > [ 14.560000] [<00038200>] parameq+0x48/0x6e > [ 14.560000] [<002c778c>] __tty_insert_flip_string_flags+0x0/0x14e > [ 14.560000] [<00051798>] vprintk_emit+0x156/0x238 > [ 14.560000] [<00051894>] vprintk_default+0x1a/0x1e > [ 14.560000] [<000529a8>] vprintk+0x74/0x86 > [ 14.560000] [<004a6596>] _printk+0x12/0x16 > [ 14.560000] [<002e23be>] pmz_receive_chars+0x1cc/0x394 > [ 14.560000] [<004b6444>] _raw_spin_lock+0x0/0x28 > [ 14.560000] [<00038226>] parse_args+0x0/0x3a6 > [ 14.560000] [<004b6466>] _raw_spin_lock+0x22/0x28 > [ 14.560000] [<002e26b4>] pmz_interrupt+0x12e/0x1e0 > [ 14.560000] [<00048680>] arch_cpu_idle_enter+0x0/0x8 > [ 14.560000] [<00054ebc>] __handle_irq_event_percpu+0x24/0x106 > [ 14.560000] [<004ae576>] default_idle_call+0x0/0x46 > [ 14.560000] [<00055020>] handle_irq_event+0x30/0x90 > [ 14.560000] [<00058320>] handle_simple_irq+0x5e/0xc0 > [ 14.560000] [<00048688>] arch_cpu_idle_exit+0x0/0x8 > [ 14.560000] [<00054800>] generic_handle_irq+0x3c/0x4a > [ 14.560000] [<00002978>] do_IRQ+0x24/0x3a > [ 14.560000] [<004ae508>] cpu_idle_poll.isra.0+0x0/0x6e > [ 14.560000] [<00002874>] auto_irqhandler_fixup+0x4/0xc > [ 14.560000] [<004ae508>] cpu_idle_poll.isra.0+0x0/0x6e > [ 14.560000] [<004ae576>] default_idle_call+0x0/0x46 > [ 14.560000] [<004ae598>] default_idle_call+0x22/0x46 > [ 14.560000] [<00048710>] do_idle+0x6a/0xf0 > [ 14.560000] [<000486a6>] do_idle+0x0/0xf0 > [ 14.560000] [<000367d2>] find_task_by_pid_ns+0x0/0x2a > [ 14.560000] [<0005d064>] __rcu_read_lock+0x0/0x12 > [ 14.560000] [<00048a5a>] cpu_startup_entry+0x18/0x1c > [ 14.560000] [<00063a06>] __rcu_read_unlock+0x0/0x26 > [ 14.560000] [<004ae65a>] kernel_init+0x0/0xfa > [ 14.560000] [<0049c5a8>] strcpy+0x0/0x1e > [ 14.560000] [<004a6584>] _printk+0x0/0x16 > [ 14.560000] [<0049c72a>] strlen+0x0/0x22 > [ 14.560000] [<006452d4>] memblock_alloc_try_nid+0x0/0x82 > [ 14.560000] [<0063939a>] arch_post_acpi_subsys_init+0x0/0x8 > [ 14.560000] [<0063991e>] console_on_rootfs+0x0/0x60 > [ 14.560000] [<00638410>] _sinittext+0x410/0xadc > [ 14.560000] First of all, please read this https://www.kernel.org/doc/html/latest/process/submitting-patches.html#backtraces-in-commit-messages and amend the commit message accordingly. > Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> > Cc: Michael Ellerman <m...@ellerman.id.au> > Cc: Nicholas Piggin <npig...@gmail.com> > Cc: Christophe Leroy <christophe.le...@csgroup.eu> > Cc: "Aneesh Kumar K.V" <aneesh.ku...@kernel.org> > Cc: "Naveen N. Rao" <naveen.n....@linux.ibm.com> > Cc: linux-m...@lists.linux-m68k.org Second, please move these Cc to be after the '---' line > Link: https://github.com/vivier/qemu-m68k/issues/44 > Link: https://lore.kernel.org/all/1078874617.9746.36.camel@gaston/ Missed Fixes tag? > Signed-off-by: Finn Thain <fth...@linux-m68k.org> > --- (here is a good location for Cc:) -- With Best Regards, Andy Shevchenko
