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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, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 07/40] rcu: Move RCU's grace-period-change code to ->gp_seq Date: Mon, 25 Jun 2018 17:08:26 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180626000841.GA15696@linux.vnet.ibm.com> References: <20180626000841.GA15696@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18062600-0052-0000-0000-00000303F3CC X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009255; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01052328; UDB=6.00539464; IPR=6.00830253; MB=3.00021855; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-26 00:07:01 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18062600-0053-0000-0000-00005D23BCCB Message-Id: <20180626000859.23572-7-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-25_11:,, 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=8.0.1-1806210000 definitions=main-1806260000 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit moves __note_gp_changes(), note_gp_changes(), and __rcu_pending() to ->gp_seq, creating new rcu_seq_completed_gp() and rcu_seq_new_gp() functions for this purpose. Signed-off-by: Paul E. McKenney [ paulmck: Reinstate "cpuend: trace as suggested by Joel Fernandes. ] --- kernel/rcu/rcu.h | 17 +++++++++++++++++ kernel/rcu/tree.c | 39 ++++++++++++++++----------------------- 2 files changed, 33 insertions(+), 23 deletions(-) diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index f0907f9f6cd0..7568a3fd0815 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -116,6 +116,23 @@ static inline bool rcu_seq_done(unsigned long *sp, unsigned long s) return ULONG_CMP_GE(READ_ONCE(*sp), s); } +/* + * Has a grace period completed since the time the old gp_seq was collected? + */ +static inline bool rcu_seq_completed_gp(unsigned long old, unsigned long new) +{ + return ULONG_CMP_LT(old, new & ~RCU_SEQ_STATE_MASK); +} + +/* + * Has a grace period started since the time the old gp_seq was collected? + */ +static inline bool rcu_seq_new_gp(unsigned long old, unsigned long new) +{ + return ULONG_CMP_LT((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK, + new); +} + /* * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally * by call_rcu() and rcu callback execution, and are therefore not part of the diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 1a3a7d402a20..a8c19363c979 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1790,24 +1790,23 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, raw_lockdep_assert_held_rcu_node(rnp); - /* Handle the ends of any preceding grace periods first. */ - if (rdp->completed == rnp->completed && - !unlikely(READ_ONCE(rdp->gpwrap))) { - - /* No grace period end, so just accelerate recent callbacks. */ - ret = rcu_accelerate_cbs(rsp, rnp, rdp); - - } else { - - /* Advance callbacks. */ - ret = rcu_advance_cbs(rsp, rnp, rdp); + if (rdp->gp_seq == rnp->gp_seq) + return false; /* Nothing to do. */ + /* Handle the ends of any preceding grace periods first. */ + if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) || + unlikely(READ_ONCE(rdp->gpwrap))) { + ret = rcu_advance_cbs(rsp, rnp, rdp); /* Advance callbacks. */ /* Remember that we saw this grace-period completion. */ rdp->completed = rnp->completed; - trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend")); + trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("cpuend")); + } else { + ret = rcu_accelerate_cbs(rsp, rnp, rdp); /* Recent callbacks. */ } - if (rdp->gpnum != rnp->gpnum || unlikely(READ_ONCE(rdp->gpwrap))) { + /* Now handle the beginnings of any new-to-this-CPU grace periods. */ + if (rcu_seq_new_gp(rdp->gp_seq, rnp->gp_seq) || + unlikely(READ_ONCE(rdp->gpwrap))) { /* * If the current grace period is waiting for this CPU, * set up to detect a quiescent state, otherwise don't @@ -1823,8 +1822,7 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, WRITE_ONCE(rdp->gpwrap, false); rcu_gpnum_ovf(rnp, rdp); } - if (rdp->gp_seq != rnp->gp_seq) - rdp->gp_seq = rnp->gp_seq; + rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */ return ret; } @@ -1836,8 +1834,7 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) local_irq_save(flags); rnp = rdp->mynode; - if ((rdp->gpnum == READ_ONCE(rnp->gpnum) && - rdp->completed == READ_ONCE(rnp->completed) && + if ((rdp->gp_seq == rcu_seq_current(&rnp->gp_seq) && !unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */ !raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */ local_irq_restore(flags); @@ -3283,12 +3280,8 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) !rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) return 1; - /* Has another RCU grace period completed? */ - if (READ_ONCE(rnp->completed) != rdp->completed) /* outside lock */ - return 1; - - /* Has a new RCU grace period started? */ - if (READ_ONCE(rnp->gpnum) != rdp->gpnum || + /* Have RCU grace period completed or started? */ + if (rcu_seq_current(&rnp->gp_seq) != rdp->gp_seq || unlikely(READ_ONCE(rdp->gpwrap))) /* outside lock */ return 1; -- 2.17.1