linux-kernel - Re: [PATCH tip/core/rcu 05/15] rcu: Add TPS() to event-traced strings

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Date:   Thu, 27 Jul 2017 21:32:59 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com
Subject: Re: [PATCH tip/core/rcu 05/15] rcu: Add TPS() to event-traced
 strings

On Mon, 24 Jul 2017 14:44:34 -0700
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:

> Strings used in event tracing need to be specially handled, for example,
> using the TPS() macro.  Without the TPS() macro, although output looks
> fine from within a running kernel, extracting traces from a crash dump
> produces garbage instead of strings.  This commit therefore adds the TPS()
> macro to some unadorned strings that were passed to event-tracing macros.
> 
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>

Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> ---
>  kernel/rcu/tree_plugin.h | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index bb9e6e43130f..14ba496a13cd 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -2073,7 +2073,7 @@ static void nocb_leader_wait(struct rcu_data *my_rdp)
>  
>  	/* Wait for callbacks to appear. */
>  	if (!rcu_nocb_poll) {
> -		trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep");
> +		trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, TPS("Sleep"));
>  		swait_event_interruptible(my_rdp->nocb_wq,
>  				!READ_ONCE(my_rdp->nocb_leader_sleep));
>  		raw_spin_lock_irqsave(&my_rdp->nocb_lock, flags);
> @@ -2083,7 +2083,7 @@ static void nocb_leader_wait(struct rcu_data *my_rdp)
>  		raw_spin_unlock_irqrestore(&my_rdp->nocb_lock, flags);
>  	} else if (firsttime) {
>  		firsttime = false; /* Don't drown trace log with "Poll"! */
> -		trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Poll");
> +		trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, TPS("Poll"));
>  	}
>  
>  	/*
> @@ -2111,7 +2111,7 @@ static void nocb_leader_wait(struct rcu_data *my_rdp)
>  			schedule_timeout_interruptible(1);
>  		} else {
>  			trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu,
> -					    "WokeEmpty");
> +					    TPS("WokeEmpty"));
>  		}
>  		goto wait_again;
>  	}
> @@ -2155,7 +2155,7 @@ static void nocb_leader_wait(struct rcu_data *my_rdp)
>  static void nocb_follower_wait(struct rcu_data *rdp)
>  {
>  	for (;;) {
> -		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "FollowerSleep");
> +		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("FollowerSleep"));
>  		swait_event_interruptible(rdp->nocb_wq,
>  					 READ_ONCE(rdp->nocb_follower_head));
>  		if (smp_load_acquire(&rdp->nocb_follower_head)) {
> @@ -2163,7 +2163,7 @@ static void nocb_follower_wait(struct rcu_data *rdp)
>  			return;
>  		}
>  		WARN_ON(signal_pending(current));
> -		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeEmpty");
> +		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WokeEmpty"));
>  	}
>  }
>  
> @@ -2198,7 +2198,7 @@ static int rcu_nocb_kthread(void *arg)
>  		rdp->nocb_follower_tail = &rdp->nocb_follower_head;
>  		raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
>  		BUG_ON(!list);
> -		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty");
> +		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WokeNonEmpty"));
>  
>  		/* Each pass through the following loop invokes a callback. */
>  		trace_rcu_batch_start(rdp->rsp->name,