lkml.org 
[lkml]   [2011]   [Dec]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Subjectprintk() vs tty_io
From
Date
Hi tty folks,

I've been poking at reducing the constraints on printk(), like make it
work under rq->lock etc..

Aside from a fwd port of the patch that abuses the console_sem.lock:
https://lkml.org/lkml/2011/6/9/298 and a few other not so very pretty
patches, I ran into the following lockdep splat (using a not so very
pretty lockdep early_printk() patch):

watchdog/0/10 is trying to acquire lock:
((console_sem).lock){-.-...}, at:
but task is already holding lock:
(&rt_rq->rt_runtime_lock){-.-...}, at:
which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #5 (&rt_rq->rt_runtime_lock){-.-...}:
-> #4 (&rq->lock){-.-.-.}:
-> #3 (&p->pi_lock){-.-.-.}:
-> #2 (&tty->write_wait){-.-...}:
-> #1 (&port_lock_key){-.-...}:
-> #0 ((console_sem).lock){-.-...}:

It turns out that writing to a console does wakeups due to tty_io.c.

My question is basically, is there a feasible way around doing these
wakeups from the console::write() path? Everything I thought of was
really quite horrible... and very likely would break stuff since I'm not
that well versed in the whole tty thing.




\
 
 \ /
  Last update: 2011-12-13 20:37    [W:0.098 / U:0.888 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site