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Date: Fri, 9 May 2014 17:37:57 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: josh@...htriplett.org
Cc: linux-kernel@...r.kernel.org, mingo@...nel.org,
laijs@...fujitsu.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
darren@...art.com, fweisbec@...il.com, oleg@...hat.com, sbw@....edu
Subject: Re: [PATCH tip/core/rcu 27/45] rcutorture: Export RCU grace-period
kthread wait state to rcutorture
On Wed, May 07, 2014 at 03:05:31PM -0700, josh@...htriplett.org wrote:
> On Mon, Apr 28, 2014 at 05:25:15PM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
> >
> > This commit allows rcutorture to print additional state for the
> > RCU grace-period kthreads in cases where RCU seems reluctant to
> > start a new grace period.
> >
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
>
> Should something reset gp_state after fqs finishes?
If I need more debugging info later on, yes. ;-)
Thanx, Paul
> Reviewed-by: Josh Triplett <josh@...htriplett.org>
>
> > include/linux/rcutiny.h | 4 ++++
> > include/linux/rcutree.h | 1 +
> > kernel/rcu/rcutorture.c | 1 +
> > kernel/rcu/tree.c | 17 +++++++++++++++++
> > kernel/rcu/tree.h | 8 +++++++-
> > 5 files changed, 30 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
> > index 425c659d54e5..d40a6a451330 100644
> > --- a/include/linux/rcutiny.h
> > +++ b/include/linux/rcutiny.h
> > @@ -119,6 +119,10 @@ static inline void rcu_sched_force_quiescent_state(void)
> > {
> > }
> >
> > +static inline void show_rcu_gp_kthreads(void)
> > +{
> > +}
> > +
> > static inline void rcu_cpu_stall_reset(void)
> > {
> > }
> > diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
> > index a59ca05fd4e3..3e2f5d432743 100644
> > --- a/include/linux/rcutree.h
> > +++ b/include/linux/rcutree.h
> > @@ -84,6 +84,7 @@ extern unsigned long rcutorture_vernum;
> > long rcu_batches_completed(void);
> > long rcu_batches_completed_bh(void);
> > long rcu_batches_completed_sched(void);
> > +void show_rcu_gp_kthreads(void);
> >
> > void rcu_force_quiescent_state(void);
> > void rcu_bh_force_quiescent_state(void);
> > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> > index 50c26a7b6d97..15af04177e7e 100644
> > --- a/kernel/rcu/rcutorture.c
> > +++ b/kernel/rcu/rcutorture.c
> > @@ -1033,6 +1033,7 @@ rcu_torture_printk(char *page)
> > "??? Writer stall state %d g%lu c%lu f%#x\n",
> > rcu_torture_writer_state,
> > gpnum, completed, flags);
> > + show_rcu_gp_kthreads();
> > rcutorture_trace_dump();
> > }
> > rtcv_snap = rcu_torture_current_version;
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 032106df7391..3107bd935b2b 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -280,6 +280,21 @@ void rcu_bh_force_quiescent_state(void)
> > EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
> >
> > /*
> > + * Show the state of the grace-period kthreads.
> > + */
> > +void show_rcu_gp_kthreads(void)
> > +{
> > + struct rcu_state *rsp;
> > +
> > + for_each_rcu_flavor(rsp) {
> > + pr_info("%s: wait state: %d ->state: %#lx\n",
> > + rsp->name, rsp->gp_state, rsp->gp_kthread->state);
> > + /* sched_show_task(rsp->gp_kthread); */
> > + }
> > +}
> > +EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads);
> > +
> > +/*
> > * Record the number of times rcutorture tests have been initiated and
> > * terminated. This information allows the debugfs tracing stats to be
> > * correlated to the rcutorture messages, even when the rcutorture module
> > @@ -1611,6 +1626,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
> > trace_rcu_grace_period(rsp->name,
> > ACCESS_ONCE(rsp->gpnum),
> > TPS("reqwait"));
> > + rsp->gp_state = RCU_GP_WAIT_GPS;
> > wait_event_interruptible(rsp->gp_wq,
> > ACCESS_ONCE(rsp->gp_flags) &
> > RCU_GP_FLAG_INIT);
> > @@ -1638,6 +1654,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
> > trace_rcu_grace_period(rsp->name,
> > ACCESS_ONCE(rsp->gpnum),
> > TPS("fqswait"));
> > + rsp->gp_state = RCU_GP_WAIT_FQS;
> > ret = wait_event_interruptible_timeout(rsp->gp_wq,
> > ((gf = ACCESS_ONCE(rsp->gp_flags)) &
> > RCU_GP_FLAG_FQS) ||
> > diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> > index 75dc3c39a02a..c2fd1e722879 100644
> > --- a/kernel/rcu/tree.h
> > +++ b/kernel/rcu/tree.h
> > @@ -406,7 +406,8 @@ struct rcu_state {
> > unsigned long completed; /* # of last completed gp. */
> > struct task_struct *gp_kthread; /* Task for grace periods. */
> > wait_queue_head_t gp_wq; /* Where GP task waits. */
> > - int gp_flags; /* Commands for GP task. */
> > + short gp_flags; /* Commands for GP task. */
> > + short gp_state; /* GP kthread sleep state. */
> >
> > /* End of fields guarded by root rcu_node's lock. */
> >
> > @@ -469,6 +470,11 @@ struct rcu_state {
> > #define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
> > #define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
> >
> > +/* Values for rcu_state structure's gp_flags field. */
> > +#define RCU_GP_WAIT_INIT 0 /* Initial state. */
> > +#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
> > +#define RCU_GP_WAIT_FQS 2 /* Wait for force-quiescent-state time. */
> > +
> > extern struct list_head rcu_struct_flavors;
> >
> > /* Sequence through rcu_state structures for each RCU flavor. */
> > --
> > 1.8.1.5
> >
>
--
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