diff options
author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2009-09-18 09:50:18 -0700 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2009-09-19 08:53:21 +0200 |
commit | e7d8842ed34a7fe19d1ed90f84c211fb056ac523 (patch) | |
tree | d49d5b8ff8829e525b8f80d60a18ef1f37e09529 /kernel/rcutree.c | |
parent | 28ecd58020409be8eb176c716f957fc3386fa2fa (diff) | |
download | lwn-e7d8842ed34a7fe19d1ed90f84c211fb056ac523.tar.gz lwn-e7d8842ed34a7fe19d1ed90f84c211fb056ac523.zip |
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>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r-- | kernel/rcutree.c | 27 |
1 files changed, 5 insertions, 22 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index e8624ebf2320..ae4a553e37ce 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -767,10 +767,10 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp, /* * Record a quiescent state for the specified CPU, which must either be - * the current CPU or an offline CPU. The lastcomp argument is used to - * make sure we are still in the grace period of interest. We don't want - * to end the current grace period based on quiescent states detected in - * an earlier grace period! + * the current CPU. The lastcomp argument is used to make sure we are + * still in the grace period of interest. We don't want to end the current + * grace period based on quiescent states detected in an earlier grace + * period! */ static void cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) @@ -805,7 +805,6 @@ cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) * This GP can't end until cpu checks in, so all of our * callbacks can be processed during the next GP. */ - rdp = rsp->rda[smp_processor_id()]; rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */ @@ -881,9 +880,6 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ - /* Being offline is a quiescent state, so go record it. */ - cpu_quiet(cpu, rsp, rdp, lastcomp); - /* * Move callbacks from the outgoing CPU to the running CPU. * Note that the outgoing CPU is now quiscent, so it is now @@ -1448,20 +1444,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) rnp = rnp->parent; } while (rnp != NULL && !(rnp->qsmaskinit & mask)); - spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ - - /* - * A new grace period might start here. If so, we will be part of - * it, and its gpnum will be greater than ours, so we will - * participate. It is also possible for the gpnum to have been - * incremented before this function was called, and the bitmasks - * to not be filled out until now, in which case we will also - * participate due to our gpnum being behind. - */ - - /* Since it is coming online, the CPU is in a quiescent state. */ - cpu_quiet(cpu, rsp, rdp, lastcomp); - local_irq_restore(flags); + spin_unlock_irqrestore(&rsp->onofflock, flags); } static void __cpuinit rcu_online_cpu(int cpu) |