lkml.org 
[lkml]   [2012]   [Mar]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 5/7] module: take rcu_read_lock_sched() for /proc read
From
Date
On Thu, 2012-03-15 at 22:48 +0800, Cong Wang wrote:
> In the seq file operations, it still hold module_mutex for just reading
> the module list, switch to rcu_read_lock_sched() too.
>

Why is it needed ?

1) insmod/rmmod/lsmod is hardly in fast path.

2) after a mutex_lock(), a task is still preemptible
after rcu_read_lock_sched(), preemption is disabled

with NR_CPUS=4096, getting module refcounts is _very_ slow

RCU doesnt fit every workload.





\
 
 \ /
  Last update: 2012-03-15 17:21    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site