Messages in this thread | | | Subject | Re: [RFC v2 4/5] rcu: Use for_each_leaf_node_cpu() in force_qs_rnp() | From | Colin Ian King <> | Date | Thu, 15 Dec 2016 14:51:36 +0000 |
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On 15/12/16 14:42, Boqun Feng wrote: > On Thu, Dec 15, 2016 at 12:04:59PM +0000, Mark Rutland wrote: >> On Thu, Dec 15, 2016 at 10:42:03AM +0800, Boqun Feng wrote: >>> ->qsmask of an RCU leaf node is usually more sparse than the >>> corresponding cpu_possible_mask. So replace the >>> for_each_leaf_node_possible_cpu() in force_qs_rnp() with >>> for_each_leaf_node_cpu() to save several checks. >>> >>> [Note we need to use "1UL << bit" instead of "1 << bit" to generate the >>> corresponding mask for a bit because @mask is unsigned long, this was >>> spotted by Colin Ian King <colin.king@canonical.com> and CoverityScan in >>> a previous version of this patch.] >> >> Nit: This note can go now that we use leaf_node_cpu_bit(). ;) >> > > I kinda keep this here for honoring the effort of finding out this bug > from Colin, but yes, it's no longer needed here for the current code.
Yep, remove it.
> > Regards, > Boqun > >> Thanks, >> Mark. >> >>> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> >>> --- >>> kernel/rcu/tree.c | 12 +++++------- >>> 1 file changed, 5 insertions(+), 7 deletions(-) >>> >>> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c >>> index 4e5b81c843de..1ef13e63bc95 100644 >>> --- a/kernel/rcu/tree.c >>> +++ b/kernel/rcu/tree.c >>> @@ -3046,13 +3046,11 @@ static void force_qs_rnp(struct rcu_state *rsp, >>> continue; >>> } >>> } >>> - for_each_leaf_node_possible_cpu(rnp, cpu) { >>> - unsigned long bit = leaf_node_cpu_bit(rnp, cpu); >>> - if ((rnp->qsmask & bit) != 0) { >>> - if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj)) >>> - mask |= bit; >>> - } >>> - } >>> + >>> + for_each_leaf_node_cpu(rnp, rnp->qsmask, cpu) >>> + if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj)) >>> + mask |= leaf_node_cpu_bit(rnp, cpu); >>> + >>> if (mask != 0) { >>> /* Idle/offline CPUs, report (releases rnp->lock. */ >>> rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); >>> -- >>> 2.10.2 >>>
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