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rcu: Apply results of code inspection of kernel/rcutree_plugin.h
o Drop the calls to cpu_quiet() from the online/offline code. These are unnecessary, since force_quiescent_state() will clean up, and removing them simplifies the code a bit. o Add a warning to check that we don't enqueue the same blocked task twice onto the ->blocked_tasks[] lists. o Rework the phase computation in rcu_preempt_note_context_switch() to be more readable, as suggested by Josh Triplett. o Disable irqs to close a race between the scheduling clock interrupt and rcu_preempt_note_context_switch() WRT the ->rcu_read_unlock_special field. o Add comments to rnp->lock acquisition and release within rcu_read_unlock_special() noting that irqs are already disabled. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu LKML-Reference: <12532926201851-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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2 changed files with 11 additions and 26 deletions
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@ -767,10 +767,10 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
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/*
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* Record a quiescent state for the specified CPU, which must either be
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* the current CPU or an offline CPU. The lastcomp argument is used to
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* make sure we are still in the grace period of interest. We don't want
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* to end the current grace period based on quiescent states detected in
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* an earlier grace period!
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* the current CPU. The lastcomp argument is used to make sure we are
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* still in the grace period of interest. We don't want to end the current
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* grace period based on quiescent states detected in an earlier grace
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* period!
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*/
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static void
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cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
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@ -805,7 +805,6 @@ cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
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* This GP can't end until cpu checks in, so all of our
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* callbacks can be processed during the next GP.
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*/
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rdp = rsp->rda[smp_processor_id()];
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rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
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cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */
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@ -881,9 +880,6 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
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spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
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/* Being offline is a quiescent state, so go record it. */
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cpu_quiet(cpu, rsp, rdp, lastcomp);
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/*
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* Move callbacks from the outgoing CPU to the running CPU.
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* Note that the outgoing CPU is now quiscent, so it is now
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@ -1448,20 +1444,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
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rnp = rnp->parent;
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} while (rnp != NULL && !(rnp->qsmaskinit & mask));
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spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
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/*
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* A new grace period might start here. If so, we will be part of
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* it, and its gpnum will be greater than ours, so we will
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* participate. It is also possible for the gpnum to have been
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* incremented before this function was called, and the bitmasks
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* to not be filled out until now, in which case we will also
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* participate due to our gpnum being behind.
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*/
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/* Since it is coming online, the CPU is in a quiescent state. */
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cpu_quiet(cpu, rsp, rdp, lastcomp);
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local_irq_restore(flags);
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spin_unlock_irqrestore(&rsp->onofflock, flags);
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}
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static void __cpuinit rcu_online_cpu(int cpu)
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