lkml.org 
[lkml]   [2014]   [Feb]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: smp_call_function_single with wait=0 considered harmful
On Wed, Dec 04, 2013 at 08:46:27AM -0800, Christoph Hellwig wrote:
> While doing my recent work on the generic smp function calls I noticed
> that smp_call_function_single without the wait flag can't work, as
> it allocates struct call_single_data on stack, and without the wait
> flag will happily return before the IPI has been executed.

It doesn't actually; it uses a per-cpu one in the !wait case.

The subsequent csd_lock() ensures it will wait for any prior user to
complete, so only if you're doing multiple smp_call_function_single()
invocations back-to-back will they queue up.

> This affects the following callers:

<snip>

> kernel/stop_machine.c:stop_two_cpus()

That site should work with .wait=1 just fine, but given the above, the
.wait=0 doesn't appear problematic at all.


\
 
 \ /
  Last update: 2014-02-28 14:01    [W:0.066 / U:0.500 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site