Re: (WARNING) possible deadlock in del_timer_sync, called from fbcon_del_cursor_timer

On Thu, Mar 3, 2011 at 2:12 AM, Steven Rostedt [off-list ref] wrote:

On Mon, Feb 28, 2011 at 03:41:07PM +0100, Clemens Ladisch wrote:

quoted

While using the FB console, I tried to change the console log level
with SysRq, and got this warning that del_timer_sync() is used in
an interrupt handler:

Ug, del_timer_sync() can be called from interrupt context:

printk -> vt_console_print -> hide_cursor -> fbcon_cursor
-> fbcon_del_cursor_time -> del_timer_sync()

printk is allowed to be called from interrupt context. This is indeed a
true bug.

Yeah.

And more explanation for that WARN_ON() :)

run_timer_softirq(SOFTIRQ context)
  cursor_timer_handler()
  Interrupt comes in(IRQ context)
    ...
      del_timer_sync()
        deadlock

So fbcon guys:
Could above situation happen?

Cc'ing people from:
./scripts/get_maintainer.pl -f drivers/video/console/fbcon.c

Thanks,
Yong


-- 
Only stand for myself