Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v2] x86/apic/vector: Move pr_warn() out of vector_lock | Date | Mon, 29 Mar 2021 22:44:11 +0200 |
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Waiman,
On Mon, Mar 29 2021 at 15:57, Waiman Long wrote: > On 3/29/21 8:42 AM, Thomas Gleixner wrote: >> On Sun, Mar 28 2021 at 20:52, Waiman Long wrote: >>> It was found that the following circular locking dependency warning >>> could happen in some systems: >>> >>> [ 218.097878] ====================================================== >>> [ 218.097879] WARNING: possible circular locking dependency detected >>> [ 218.097880] 4.18.0-228.el8.x86_64+debug #1 Not tainted >> Reports have to be against latest mainline and not against the random >> distro frankenkernel of the day. That's nothing new. >> >> Plus I was asking you to provide a full splat to look at so this can be >> discussed _upfront_. Oh well... > > That was the full splat that I can see except the following trailing > data:
I meant: Just the splat without yet another eyebleeding patch.
>>> [ 218.097985] 6 locks held by systemd/1: >>> [ 218.097986] #0: ffff88822b5cc1e8 (&tty->legacy_mutex){+.+.}, at: tty_init_dev+0x79/0x440 >>> [ 218.097989] #1: ffff88832ee00770 (&port->mutex){+.+.}, at: tty_port_open+0x85/0x190 >>> [ 218.097993] #2: ffff88813be85a88 (&desc->request_mutex){+.+.}, at: __setup_irq+0x249/0x1e60 >>> [ 218.097996] #3: ffff88813be858c0 (&irq_desc_lock_class){-.-.}, at: __setup_irq+0x2d9/0x1e60 >>> [ 218.098000] #4: ffffffff84afca78 (vector_lock){-.-.}, at: x86_vector_activate+0xca/0xab0 >>> [ 218.098003] #5: ffffffff84c27e20 (console_lock){+.+.}, at: vprintk_emit+0x13a/0x450 >> This is a more fundamental problem than just vector lock and the same >> problem exists with any other printk over serial which is nested in the >> interrupt activation chain not only on X86. > > That is true. This problem is more generic than just that. I am hoping > that the new printk rewrite may address this problem. I have been > waiting for a while and that work is still not upstream yet. So what is > your current timeline for that? If that will happen soon, I probably > don't need this patch. I send this patch out as I am uncertain about > it.
Timeline? You know how kernel development works, right?
>> But, because I'm curious and printk is a constant source of trouble, I >> just added unconditional pr_warns into those functions under vector_lock >> on 5.12-rc5. >> >> Still waiting for the lockdep splat to show up while enjoying the >> trickle of printks over serial. >> >> If you really think this is an upstream problem then please provide a >> corresponding lockdep splat on plain 5.12-rc5 along with a .config and >> the scenario which triggers this. Not less, not more. > > I will try to reproduce this problem with an upstream kernel.
Yes please.
Thanks,
tglx
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