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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-03-10 17:55:52 (GMT) |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-04-29 15:43:32 (GMT) |
| commit | 365187fbc04fd55766bf6a94e37e558505bf480a (patch) | |
| tree | 6249491e31d2c9e6e1fdb62048694b28f0974d97 /kernel/rcu/tree.c | |
| parent | 83ebe63ead0fe60e4b548730800cb68293ce098b (diff) | |
| download | linux-365187fbc04fd55766bf6a94e37e558505bf480a.tar.xz | |
rcu: Update cpu_needs_another_gp() for futures from non-NOCB CPUs
In the old days, the only source of requests for future grace periods
was NOCB CPUs. This has changed: CPUs routinely post requests for
future grace periods in order to promote power efficiency and reduce
OS jitter with minimal impact on grace-period latency. This commit
therefore updates cpu_needs_another_gp() to invoke rcu_future_needs_gp()
instead of rcu_nocb_needs_gp(). The latter is no longer used, so is
now removed. This commit also adds tracing for the irq_work_queue()
wakeup case.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 39 |
1 files changed, 29 insertions, 10 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index b33c29a..b468899 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -324,6 +324,28 @@ cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) } /* + * Return the root node of the specified rcu_state structure. + */ +static struct rcu_node *rcu_get_root(struct rcu_state *rsp) +{ + return &rsp->node[0]; +} + +/* + * Is there any need for future grace periods? + * Interrupts must be disabled. If the caller does not hold the root + * rnp_node structure's ->lock, the results are advisory only. + */ +static int rcu_future_needs_gp(struct rcu_state *rsp) +{ + struct rcu_node *rnp = rcu_get_root(rsp); + int idx = (ACCESS_ONCE(rnp->completed) + 1) & 0x1; + int *fp = &rnp->need_future_gp[idx]; + + return ACCESS_ONCE(*fp); +} + +/* * Does the current CPU require a not-yet-started grace period? * The caller must have disabled interrupts to prevent races with * normal callback registry. @@ -335,7 +357,7 @@ cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) if (rcu_gp_in_progress(rsp)) return 0; /* No, a grace period is already in progress. */ - if (rcu_nocb_needs_gp(rsp)) + if (rcu_future_needs_gp(rsp)) return 1; /* Yes, a no-CBs CPU needs one. */ if (!rdp->nxttail[RCU_NEXT_TAIL]) return 0; /* No, this is a no-CBs (or offline) CPU. */ @@ -350,14 +372,6 @@ cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) } /* - * Return the root node of the specified rcu_state structure. - */ -static struct rcu_node *rcu_get_root(struct rcu_state *rsp) -{ - return &rsp->node[0]; -} - -/* * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state * * If the new value of the ->dynticks_nesting counter now is zero, @@ -1672,6 +1686,8 @@ static void rsp_wakeup(struct irq_work *work) /* Wake up rcu_gp_kthread() to start the grace period. */ wake_up(&rsp->gp_wq); + trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum), + "Workqueuewoken"); } /* @@ -1706,8 +1722,11 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, * the wakeup to interrupt context. And don't bother waking * up the running kthread. */ - if (current != rsp->gp_kthread) + if (current != rsp->gp_kthread) { + trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum), + "Workqueuewake"); irq_work_queue(&rsp->wakeup_work); + } } /* |