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Message-ID: <20140507220531.GO27924@cloud>
Date: Wed, 7 May 2014 15:05:31 -0700
From: josh@...htriplett.org
To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
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 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?
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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