On Tue, Oct 08, 2019 at 06:35:45PM +0200, Marco Elver wrote: > On Tue, 8 Oct 2019 at 18:30, Joel Fernandes <j...@joelfernandes.org> wrote: > > > > On Tue, Oct 08, 2019 at 01:01:40PM +0800, Boqun Feng wrote: > > > "mask_ofl_ipi" is used for iterate CPUs which IPIs are needed to send > > > to, however in the IPI sending loop, "mask_ofl_ipi" along with another > > > variable "mask_ofl_test" might also get modified to record which CPU's > > > quiesent state can be reported by sync_rcu_exp_select_node_cpus(). Two > > > variables seems to be redundant for such a propose, so this patch clean > > > things a little by solely using "mask_ofl_test" for recording and > > > "mask_ofl_ipi" for iteration. This would improve the readibility of the > > > IPI sending loop in sync_rcu_exp_select_node_cpus(). > > > > > > Signed-off-by: Boqun Feng <boqun.f...@gmail.com> > > > --- > > > > Reviewed-by: Joel Fernandes (Google) <j...@joelfernandes.org> > > > > thanks, > > > > - Joel > > Acked-by: Marco Elver <el...@google.com> > > If this is the official patch for the fix to the KCSAN reported > data-race, it'd be great to include the tag: > Reported-by: syzbot+134336b86f728d6e5...@syzkaller.appspotmail.com > so the bot knows this was fixed.
I applied your Acked-by to both patches, but please let me know if you intended something else. Either way, thank you both for finding this and for your testing! Thanx, Paul > Thanks! > -- Marco > > > > kernel/rcu/tree_exp.h | 13 ++++++------- > > > 1 file changed, 6 insertions(+), 7 deletions(-) > > > > > > diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h > > > index 69c5aa64fcfd..212470018752 100644 > > > --- a/kernel/rcu/tree_exp.h > > > +++ b/kernel/rcu/tree_exp.h > > > @@ -387,10 +387,10 @@ static void sync_rcu_exp_select_node_cpus(struct > > > work_struct *wp) > > > } > > > ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, > > > 0); > > > put_cpu(); > > > - if (!ret) { > > > - mask_ofl_ipi &= ~mask; > > > + /* The CPU responses the IPI, and will report QS itself */ > > > + if (!ret) > > > continue; > > > - } > > > + > > > /* Failed, raced with CPU hotplug operation. */ > > > raw_spin_lock_irqsave_rcu_node(rnp, flags); > > > if ((rnp->qsmaskinitnext & mask) && > > > @@ -401,13 +401,12 @@ static void sync_rcu_exp_select_node_cpus(struct > > > work_struct *wp) > > > schedule_timeout_uninterruptible(1); > > > goto retry_ipi; > > > } > > > - /* CPU really is offline, so we can ignore it. */ > > > - if (!(rnp->expmask & mask)) > > > - mask_ofl_ipi &= ~mask; > > > + /* CPU really is offline, and we need its QS to pass GP. */ > > > + if (rnp->expmask & mask) > > > + mask_ofl_test |= mask; > > > raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > > > } > > > /* Report quiescent states for those that went offline. */ > > > - mask_ofl_test |= mask_ofl_ipi; > > > if (mask_ofl_test) > > > rcu_report_exp_cpu_mult(rnp, mask_ofl_test, false); > > > } > > > -- > > > 2.23.0 > > >