lkml.org 
[lkml]   [2014]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/1] rcu: Check for have_rcu_nocb_mask instead of rcu_nocb_mask
On Thu, Jul 17, 2014 at 05:30:11PM -0400, Pranith Kumar wrote:
> Hi Paul,
>
> This is something similar to what you found yesterday with tick_nohz_full mask.
>
> --
> Pranith
>
> If we configure a kernel with CONFIG_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_NONE=y and
> CONFIG_CPUMASK_OFFSTACK=n and do not pass in a rcu_nocb= boot parameter, the
> cpumask rcu_nocb_mask can be garbage instead of NULL.
>
> Hence this commit replaces checks for rcu_nocb_mask == NULL with a check for
> have_rcu_nocb_mask.
>
> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>

Good catch! Could you please forward-port this to current rcu/dev?
This now includes the fix you mentioned above, which generates conflicts.

Could you please also fix the use in rcu_is_nocb_cpu()?

And please see the comment below.

Thanx, Paul

> ---
> kernel/rcu/tree_plugin.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index cedb020..15c00b5 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -2542,7 +2542,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp)
> struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */
> struct rcu_data *rdp_prev = NULL;
>
> - if (rcu_nocb_mask == NULL)
> + if (!have_rcu_nocb_mask)
> return;
> #ifdef CONFIG_NO_HZ_FULL
> cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask);
> @@ -2575,7 +2575,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp)
> /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */
> static bool init_nocb_callback_list(struct rcu_data *rdp)
> {
> - if (rcu_nocb_mask == NULL ||
> + if (have_rcu_nocb_mask == false ||

This should really be "if (!have_rcu_nocb_mask".

Of course, the original should have been "if (!rcu_nocb_mask", but old
habits die hard. ;-)

> !cpumask_test_cpu(rdp->cpu, rcu_nocb_mask))
> return false;
> rdp->nxttail[RCU_NEXT_TAIL] = NULL;
> --
> 1.9.1
>



\
 
 \ /
  Last update: 2014-07-18 02:41    [W:0.075 / U:0.536 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site