lkml.org 
[lkml]   [2019]   [Jun]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] kernel/isolation: Assert that a housekeeping CPU comes up at boot time
On 06/25/19 10:17, Nicholas Piggin wrote:
> With the change to allow the boot CPU0 to be isolated, it is possible
> to specify command line options that result in no housekeeping CPU
> online at boot.
>
> An 8 CPU system booted with "nohz_full=0-6 maxcpus=4", for example.
>
> It is not easily possible at housekeeping init time to know all the
> various SMP options that will result in an invalid configuration, so
> this patch adds a sanity check after SMP init, to ensure that a
> housekeeping CPU has been onlined.
>
> The panic is undesirable, but it's better than the alternative of an
> obscure non deterministic failure. The panic will reliably happen
> when advanced parameters are used incorrectly.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
> v2: Fix a NULL pointer dereference when not overriding housekeeping,
> noticed by kernel test robot and Qais, who fixed it and verified
> the fix (thanks!)

Glad I could help. But for the record my problem wasn't a NULL pointer
dereference and simply the loop didn't hit the condition to 'return 0' so I hit
the panic.

I tested that the fix does indeed skip the verification if no nohz_full nor
isolcpus is passed. But I didn't do the reverse check, although from the code
this flag is only set in housekeeping_setup() so it should continue to work as
intended.

Thanks!

--
Qais Yousef

\
 
 \ /
  Last update: 2019-06-25 11:28    [W:0.033 / U:21.804 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site