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McKenney" To: Steven Rostedt Cc: Byungchul Park , jiangshanlai@gmail.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org, kernel-team@lge.com, joel@joelfernandes.org Subject: Re: [RFC 1/2] rcu: Do prepare and cleanup idle depending on in_nmi() Reply-To: paulmck@linux.vnet.ibm.com References: <1529484440-20634-1-git-send-email-byungchul.park@lge.com> <20180620093309.7d07715a@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180620093309.7d07715a@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18062014-0072-0000-0000-000003722D67 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009227; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000265; SDB=6.01049754; UDB=6.00537917; IPR=6.00828727; MB=3.00021760; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-20 14:56:42 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18062014-0073-0000-0000-0000486D794A Message-Id: <20180620145840.GR3593@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-20_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=984 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1805220000 definitions=main-1806200164 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 20, 2018 at 09:33:09AM -0400, Steven Rostedt wrote: > On Wed, 20 Jun 2018 17:47:19 +0900 > Byungchul Park wrote: > > > Get rid of dependency on ->dynticks_nmi_nesting. > > This is not a trivial change. Can you please explain the rational and > background in the change log. Add enough context here to know why this > change is needed. What Steve said!!! Thanx, Paul > Thanks! > > -- Steve > > > > > Signed-off-by: Byungchul Park > > --- > > kernel/rcu/tree.c | 22 ++++++++++------------ > > 1 file changed, 10 insertions(+), 12 deletions(-) > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index deb2508..59ae94e 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -797,6 +797,11 @@ void rcu_nmi_exit(void) > > return; > > } > > > > + if (!in_nmi()) { > > + rcu_prepare_for_idle(); > > + rcu_dynticks_task_enter(); > > + } > > + > > /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ > > trace_rcu_dyntick(TPS("Startirq"), rdtp->dynticks_nmi_nesting, 0, rdtp->dynticks); > > WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ > > @@ -824,14 +829,8 @@ void rcu_nmi_exit(void) > > */ > > void rcu_irq_exit(void) > > { > > - struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); > > - > > lockdep_assert_irqs_disabled(); > > - if (rdtp->dynticks_nmi_nesting == 1) > > - rcu_prepare_for_idle(); > > rcu_nmi_exit(); > > - if (rdtp->dynticks_nmi_nesting == 0) > > - rcu_dynticks_task_enter(); > > } > > > > /* > > @@ -944,6 +943,11 @@ void rcu_nmi_enter(void) > > if (rcu_dynticks_curr_cpu_in_eqs()) { > > rcu_dynticks_eqs_exit(); > > incby = 1; > > + > > + if (!in_nmi()) { > > + rcu_dynticks_task_exit(); > > + rcu_cleanup_after_idle(); > > + } > > } > > trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="), > > rdtp->dynticks_nmi_nesting, > > @@ -977,14 +981,8 @@ void rcu_nmi_enter(void) > > */ > > void rcu_irq_enter(void) > > { > > - struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); > > - > > lockdep_assert_irqs_disabled(); > > - if (rdtp->dynticks_nmi_nesting == 0) > > - rcu_dynticks_task_exit(); > > rcu_nmi_enter(); > > - if (rdtp->dynticks_nmi_nesting == 1) > > - rcu_cleanup_after_idle(); > > } > > > > /* >