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McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org Subject: Re: [PATCH tip/core/rcu 0/19] RCU flavor-consolidation changes for v4.20/v5.0 Reply-To: paulmck@linux.vnet.ibm.com References: <20180829222021.GA29944@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180829222021.GA29944@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18082922-0072-0000-0000-000003996727 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009636; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01080739; UDB=6.00557494; IPR=6.00860724; MB=3.00023001; MTD=3.00000008; XFM=3.00000015; UTC=2018-08-29 22:22:18 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18082922-0073-0000-0000-0000493EABFA Message-Id: <20180829222214.GA19014@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-08-29_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1808290217 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 29, 2018 at 03:20:21PM -0700, Paul E. McKenney wrote: > Hello! > > This series contains the RCU flavor consolidation, along with some initial > cleanup work enabled by that consolidation (and some that became apparent > while cleaning up): > > 1. Refactor rcu_{nmi,irq}_{enter,exit}(), saving a branch on the > idle entry/exit hotpaths, courtesy of Byungchul Park, > > 2. Defer reporting RCU-preempt quiescent states when disabled. > This is the key commit that consolidates the RCU-bh and RCU-sched > flavors into RCU, however, the RCU-bh and RCU-sched flavors > still exist independently as well at this point. > > 3. Test extended "rcu" read-side critical sections. This commit > causes rcutorture to test RCU's new-found ability to act as > the combination of RCU, RCU-bh, and RCU-sched. > > 4. Allow processing deferred QSes for exiting RCU-preempt readers. > This is a optimization. > > 5. Remove now-unused ->b.exp_need_qs field from the rcu_special union. > > 6. Add warning to detect half-interrupts. Test the claim that > the Linux kernel no longer does half-interrupts. > > 7. Apply RCU-bh QSes to RCU-sched and RCU-preempt when safe, that is, > make the consolidated RCU inherit RCU-bh's denial-of-service > avoidance mechanism. > > 8. Report expedited grace periods at context-switch time. This is > an optimization enabled by the RCU flavor consolidation. > > 9. Define RCU-bh update API in terms of RCU. This commit gets rid > of the RCU-bh update mechanism. > > 10. Update comments and help text to account for the removal of > the RCU-bh update mechanism. > > 11. Drop "wake" parameter from rcu_report_exp_rdp(). > > 12. Fix typo in rcu_get_gp_kthreads_prio() header comment. > > 13. Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds. > Although this commit gets rid of the RCU-sched update mechanism > from PREEMPT builds, it of course remains as the sole RCU flavor > for !PREEMPT && !SMP builds. > > 14. Express Tiny RCU updates in terms of RCU rather than RCU-sched. > This will enable additional cleanups and code savings. > > 15. Remove RCU_STATE_INITIALIZER() in favor of just using an open-coded > initializer for the sole remaining rcu_state structure. > > 16. Eliminate rcu_state structure's ->call field, as it is now always > just call_rcu(). > > 17. Remove rcu_state structure's ->rda field, as there is now only one > set of per-CPU rcu_data structures. And last, but perhaps not least: 18. Remove rcu_state_p pointer to default rcu_state structure, now that there is only one rcu_state structure. 19. Remove rcu_data_p pointer to default rcu_data structure, now that there is only one set of per-CPU rcu_data structures. Thanx, Paul > ------------------------------------------------------------------------ > > Documentation/RCU/Design/Requirements/Requirements.html | 50 - > include/linux/rcupdate.h | 48 - > include/linux/rcupdate_wait.h | 6 > include/linux/rcutiny.h | 61 + > include/linux/rcutree.h | 31 > include/linux/sched.h | 6 > kernel/rcu/Kconfig | 10 > kernel/rcu/rcutorture.c | 1 > kernel/rcu/tiny.c | 163 +-- > kernel/rcu/tree.c | 655 +++++----------- > kernel/rcu/tree.h | 44 - > kernel/rcu/tree_exp.h | 256 +++--- > kernel/rcu/tree_plugin.h | 523 ++++++------ > kernel/rcu/update.c | 2 > kernel/softirq.c | 3 > 15 files changed, 836 insertions(+), 1023 deletions(-)