From: Ming Lei <ming.lei@canonical.com>
To: Scot Doyle <lkml14@scotdoyle.com>
Cc: Pavel Machek <pavel@ucw.cz>,
Tomi Valkeinen <tomi.valkeinen@ti.com>,
Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
David Daney <david.daney@cavium.com>,
Dann Frazier <dann.frazier@canonical.com>,
Jeremy Kerr <jk@ozlabs.org>,
Peter Hurley <peter@hurleysoftware.com>,
Jonathan Liu <net147@gmail.com>,
Alistair Popple <alistair@popple.id.au>,
Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
"Chintakuntla, Radha" <Radha.Chintakuntla@caviumnetworks.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>, David Airlie <airlied@linux.ie>,
dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] fbcon: use default if cursor blink interval is not valid
Date: Thu, 19 May 2016 23:31:43 +0800 [thread overview]
Message-ID: <CACVXFVOQymQ1HdPOMdB8cZ_Bas-fChPR3-ffhCWAWGxYhkWKBA@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1605190903170.13857@laptop>
On Thu, May 19, 2016 at 10:22 PM, Scot Doyle <lkml14@scotdoyle.com> wrote:
> On Thu, 19 May 2016, Pavel Machek wrote:
>> Hi!
>>
>> > Two current [1] and three previous [2] systems locked during boot
>> > because the cursor flash timer was set using an ops->cur_blink_jiffies
>> > value of 0. Previous patches attempted to solve the problem by moving
>> > variable initialization earlier in the setup sequence [2].
>> >
>> > Use the normal cursor blink default interval of 200 ms if
>> > ops->cur_blink_jiffies is not in the range specified in commit
>> > bd63364caa8d. Since invalid values are not used, specific system
>> > initialization timings should not cause lockups.
>> >
>> > [1] https://bugs.launchpad.net/bugs/1574814
>> > [2] see commits: 2a17d7e80f1d, f235f664a8af, a1e533ec07d5
>>
>> Acked-by: Pavel Machek <pavel@ucw.cz>
>>
>> > static void cursor_timer_handler(unsigned long dev_addr)
>> > {
>> > struct fb_info *info = (struct fb_info *) dev_addr;
>> > struct fbcon_ops *ops = info->fbcon_par;
>> >
>> > queue_work(system_power_efficient_wq, &info->queue);
>> > - mod_timer(&ops->cursor_timer, jiffies + ops->cur_blink_jiffies);
>> > + mod_timer(&ops->cursor_timer, jiffies +
>> > + cursor_blink_jiffies(ops->cur_blink_jiffies));
>> > }
>> >
>> > static void fbcon_add_cursor_timer(struct fb_info *info)
>>
>> And actually... perhaps mod_timer should have some check for too low
>> timeouts..?
>>
>> WARN_ON?
>> Pavel
>
>
> Interesting idea. I applied this patch to a couple systems and
> receive the same warning on both:
If 'jiffies' is passed to mod_timer() for same timer unusually OR
mod_timer() isn't called from the timer handler, it shoudln't cause
soft lockup.
In the case of fbcon, 'jiffies' is always passed to mod_timer() and
mod_timer() is called from the timer handler meantime, that is a
real lockup.
>
> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> index 73164c3..f6c0b69 100644
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -788,6 +788,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
>
> timer_stats_timer_set_start_info(timer);
> BUG_ON(!timer->function);
> + WARN_ONCE(expires == jiffies, "timer should expire in the future");
>
> base = lock_timer_base(timer, &flags);
>
> ------
>
> [ 2.060474] ------------[ cut here ]------------
> [ 2.061613] WARNING: CPU: 0 PID: 164 at kernel/time/timer.c:791 mod_timer+0x233/0x240
> [ 2.062740] timer should expire in the future
> [ 2.062757] CPU: 0 PID: 164 Comm: kworker/0:2 Not tainted 4.6.0+ #7
> [ 2.065870] Hardware name: Toshiba Leon, BIOS 12/04/2013
> [ 2.067828] Workqueue: events_power_efficient hub_init_func3
> [ 2.069762] 0000000000000000 ffff88007443bbb8 ffffffff8139932b ffff88007443bc08
> [ 2.071701] 0000000000000000 ffff88007443bbf8 ffffffff8112e57c 0000031700000000
> [ 2.073655] ffff88007486a0b0 00000000fffea2da ffff88007486a000 0000000000000202
> [ 2.075594] Call Trace:
> [ 2.077503] [<ffffffff8139932b>] dump_stack+0x4d/0x72
> [ 2.079426] [<ffffffff8112e57c>] __warn+0xcc/0xf0
> [ 2.081325] [<ffffffff8112e5ef>] warn_slowpath_fmt+0x4f/0x60
> [ 2.083212] [<ffffffff813ad5e5>] ? find_next_bit+0x15/0x20
> [ 2.085022] [<ffffffff8139914f>] ? cpumask_next_and+0x2f/0x40
> [ 2.086696] [<ffffffff81188a93>] mod_timer+0x233/0x240
> [ 2.088362] [<ffffffff815fff02>] usb_hcd_submit_urb+0x3f2/0x8c0
> [ 2.090026] [<ffffffff81601dc4>] ? urb_destroy+0x24/0x30
> [ 2.091698] [<ffffffff81142ba8>] ? insert_work+0x58/0xb0
> [ 2.093349] [<ffffffff81602297>] usb_submit_urb+0x287/0x530
> [ 2.094985] [<ffffffff815f986d>] hub_activate+0x1fd/0x5d0
> [ 2.096625] [<ffffffff81150188>] ? finish_task_switch+0x78/0x1f0
> [ 2.098268] [<ffffffff815f9cca>] hub_init_func3+0x1a/0x20
> [ 2.099908] [<ffffffff811438e0>] process_one_work+0x140/0x3e0
> [ 2.101539] [<ffffffff81143bce>] worker_thread+0x4e/0x480
> [ 2.103173] [<ffffffff81143b80>] ? process_one_work+0x3e0/0x3e0
> [ 2.104790] [<ffffffff81143b80>] ? process_one_work+0x3e0/0x3e0
> [ 2.106259] [<ffffffff81149829>] kthread+0xc9/0xe0
> [ 2.107731] [<ffffffff81856152>] ret_from_fork+0x22/0x40
> [ 2.109215] [<ffffffff81149760>] ? __kthread_parkme+0x70/0x70
> [ 2.110704] ---[ end trace 3519886a1a990d99 ]---
>
> mod_timer is called from over a thousand places. Should timers always
> expire in the future?
>
next prev parent reply other threads:[~2016-05-19 15:31 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-17 18:41 [PATCH] tty: vt: Fix soft lockup in fbcon cursor blink timer David Daney
2016-05-17 20:49 ` Pavel Machek
2016-05-18 0:42 ` Ming Lei
2016-05-18 20:24 ` Scot Doyle
2016-05-18 20:38 ` David Daney
2016-05-19 4:21 ` [PATCH] fbcon: use default if cursor blink interval is not valid Scot Doyle
2016-05-19 7:25 ` Jeremy Kerr
2016-05-19 8:29 ` Ming Lei
2016-05-19 9:01 ` Pavel Machek
2016-05-19 14:22 ` Scot Doyle
2016-05-19 15:31 ` Ming Lei [this message]
2016-05-19 15:59 ` David Daney
2016-05-19 22:25 ` Scot Doyle
2016-05-19 22:31 ` [PATCH] fbcon: warn on invalid cursor blink intervals Scot Doyle
2016-05-19 22:50 ` David Daney
2016-05-20 1:21 ` Jeremy Kerr
2016-05-20 2:17 ` Ming Lei
2016-05-20 2:26 ` Jeremy Kerr
2016-05-20 2:48 ` Ming Lei
2016-05-20 5:04 ` Jeremy Kerr
2016-05-20 16:27 ` Scot Doyle
2016-05-24 1:19 ` Scot Doyle
2016-05-28 11:48 ` Henrique de Moraes Holschuh
2016-06-12 5:05 ` Chintakuntla, Radha
2016-05-28 11:45 ` Henrique de Moraes Holschuh
2016-05-19 0:27 ` [PATCH] tty: vt: Fix soft lockup in fbcon cursor blink timer Ming Lei
2016-05-19 7:08 ` Pavel Machek
2016-05-19 22:35 ` Scot Doyle
2016-05-28 11:44 ` Henrique de Moraes Holschuh
2016-06-14 16:22 ` Ping: " David Daney
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