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[PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for ->gp_state

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  [PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for ->gp_state "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-05 01:30 +0100
    Re: [PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for  ->gp_state Josh Triplett <josh@joshtriplett.org> - 2015-12-05 02:10 +0100
      Re: [PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for  ->gp_state Josh Triplett <josh@joshtriplett.org> - 2015-12-06 03:00 +0100
      Re: [PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for  ->gp_state "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-12-06 03:00 +0100

#1284382 — [PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for ->gp_state

Currently, ->gp_state is printed as an integer, which slows debugging.
This commit therefore prints a symbolic name in addition to the integer.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ Updated to fix relational operator called out by Dan Carpenter. ]
---
 kernel/rcu/tree.c | 15 +++++++++++++--
 kernel/rcu/tree.h |  9 +++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7b78c88e19a3..491c99a73996 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1187,6 +1187,16 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
 }
 
 /*
+ * Convert a ->gp_state value to a character string.
+ */
+static char *gp_state_getname(short gs)
+{
+	if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names))
+		return "???";
+	return gp_state_names[gs];
+}
+
+/*
  * Complain about starvation of grace-period kthread.
  */
 static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
@@ -1197,10 +1207,11 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
 	j = jiffies;
 	gpa = READ_ONCE(rsp->gp_activity);
 	if (j - gpa > 2 * HZ) {
-		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n",
+		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx\n",
 		       rsp->name, j - gpa,
 		       rsp->gpnum, rsp->completed,
-		       rsp->gp_flags, rsp->gp_state,
+		       rsp->gp_flags,
+		       gp_state_getname(rsp->gp_state), rsp->gp_state,
 		       rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
 		if (rsp->gp_kthread)
 			sched_show_task(rsp->gp_kthread);
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index f32bebb6bc90..f0304988e3f8 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -544,6 +544,15 @@ struct rcu_state {
 #define RCU_GP_DOING_FQS 4	/* Wait done for force-quiescent-state time. */
 #define RCU_GP_CLEANUP   5	/* Grace-period cleanup started. */
 #define RCU_GP_CLEANED   6	/* Grace-period cleanup complete. */
+static char * const gp_state_names[] = {
+	"RCU_GP_IDLE",
+	"RCU_GP_WAIT_GPS",
+	"RCU_GP_DONE_GPS",
+	"RCU_GP_WAIT_FQS",
+	"RCU_GP_DOING_FQS",
+	"RCU_GP_CLEANUP",
+	"RCU_GP_CLEANED",
+};
 
 extern struct list_head rcu_struct_flavors;
 
-- 
2.5.2

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#1284423 — Re: [PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for ->gp_state

On Fri, Dec 04, 2015 at 04:23:50PM -0800, Paul E. McKenney wrote:
> Currently, ->gp_state is printed as an integer, which slows debugging.
> This commit therefore prints a symbolic name in addition to the integer.
> 
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> [ Updated to fix relational operator called out by Dan Carpenter. ]
> ---
>  kernel/rcu/tree.c | 15 +++++++++++++--
>  kernel/rcu/tree.h |  9 +++++++++
>  2 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 7b78c88e19a3..491c99a73996 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1187,6 +1187,16 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
>  }
>  
>  /*
> + * Convert a ->gp_state value to a character string.
> + */
> +static char *gp_state_getname(short gs)

Same comment about "const char *"

> +{
> +	if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names))
> +		return "???";
> +	return gp_state_names[gs];
> +}
> +
> +/*
>   * Complain about starvation of grace-period kthread.
>   */
>  static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
> @@ -1197,10 +1207,11 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
>  	j = jiffies;
>  	gpa = READ_ONCE(rsp->gp_activity);
>  	if (j - gpa > 2 * HZ) {
> -		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n",
> +		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx\n",
>  		       rsp->name, j - gpa,
>  		       rsp->gpnum, rsp->completed,
> -		       rsp->gp_flags, rsp->gp_state,
> +		       rsp->gp_flags,
> +		       gp_state_getname(rsp->gp_state), rsp->gp_state,
>  		       rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
>  		if (rsp->gp_kthread)
>  			sched_show_task(rsp->gp_kthread);
> diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> index f32bebb6bc90..f0304988e3f8 100644
> --- a/kernel/rcu/tree.h
> +++ b/kernel/rcu/tree.h
> @@ -544,6 +544,15 @@ struct rcu_state {
>  #define RCU_GP_DOING_FQS 4	/* Wait done for force-quiescent-state time. */
>  #define RCU_GP_CLEANUP   5	/* Grace-period cleanup started. */
>  #define RCU_GP_CLEANED   6	/* Grace-period cleanup complete. */
> +static char * const gp_state_names[] = {

Same comment about "const char * const", but also, should this really go
in a header file?  Do any circumstances exist where this header could
get included in more than one source file in a given build?  If so,
multiple copies of this array could potentially end up in the binary, if
the compiler fails to merge them.

> +	"RCU_GP_IDLE",
> +	"RCU_GP_WAIT_GPS",
> +	"RCU_GP_DONE_GPS",
> +	"RCU_GP_WAIT_FQS",
> +	"RCU_GP_DOING_FQS",
> +	"RCU_GP_CLEANUP",
> +	"RCU_GP_CLEANED",
> +};
>  
>  extern struct list_head rcu_struct_flavors;
>  
> -- 
> 2.5.2
> 
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#1284682 — Re: [PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for ->gp_state

On Sat, Dec 05, 2015 at 05:54:36PM -0800, Paul E. McKenney wrote:
> On Fri, Dec 04, 2015 at 05:04:21PM -0800, Josh Triplett wrote:
> > On Fri, Dec 04, 2015 at 04:23:50PM -0800, Paul E. McKenney wrote:
> > > Currently, ->gp_state is printed as an integer, which slows debugging.
> > > This commit therefore prints a symbolic name in addition to the integer.
> > > 
> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > > [ Updated to fix relational operator called out by Dan Carpenter. ]
> > > ---
> > >  kernel/rcu/tree.c | 15 +++++++++++++--
> > >  kernel/rcu/tree.h |  9 +++++++++
> > >  2 files changed, 22 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > > index 7b78c88e19a3..491c99a73996 100644
> > > --- a/kernel/rcu/tree.c
> > > +++ b/kernel/rcu/tree.c
> > > @@ -1187,6 +1187,16 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
> > >  }
> > >  
> > >  /*
> > > + * Convert a ->gp_state value to a character string.
> > > + */
> > > +static char *gp_state_getname(short gs)
> > 
> > Same comment about "const char *"
> 
> Good point, fixed!
> 
> > > +{
> > > +	if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names))
> > > +		return "???";
> > > +	return gp_state_names[gs];
> > > +}
> > > +
> > > +/*
> > >   * Complain about starvation of grace-period kthread.
> > >   */
> > >  static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
> > > @@ -1197,10 +1207,11 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
> > >  	j = jiffies;
> > >  	gpa = READ_ONCE(rsp->gp_activity);
> > >  	if (j - gpa > 2 * HZ) {
> > > -		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n",
> > > +		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx\n",
> > >  		       rsp->name, j - gpa,
> > >  		       rsp->gpnum, rsp->completed,
> > > -		       rsp->gp_flags, rsp->gp_state,
> > > +		       rsp->gp_flags,
> > > +		       gp_state_getname(rsp->gp_state), rsp->gp_state,
> > >  		       rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
> > >  		if (rsp->gp_kthread)
> > >  			sched_show_task(rsp->gp_kthread);
> > > diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> > > index f32bebb6bc90..f0304988e3f8 100644
> > > --- a/kernel/rcu/tree.h
> > > +++ b/kernel/rcu/tree.h
> > > @@ -544,6 +544,15 @@ struct rcu_state {
> > >  #define RCU_GP_DOING_FQS 4	/* Wait done for force-quiescent-state time. */
> > >  #define RCU_GP_CLEANUP   5	/* Grace-period cleanup started. */
> > >  #define RCU_GP_CLEANED   6	/* Grace-period cleanup complete. */
> > > +static char * const gp_state_names[] = {
> > 
> > Same comment about "const char * const", but also, should this really go
> > in a header file?  Do any circumstances exist where this header could
> > get included in more than one source file in a given build?  If so,
> > multiple copies of this array could potentially end up in the binary, if
> > the compiler fails to merge them.
> 
> I added the const.
> 
> However, I left the array in the .h file.  The issue is that the #defines
> really have to be in the tree.h file.  Given that, if I move the array
> elsewhere, they will very likely drift out of sync.  So this sounds like
> a job for the compiler/linker...
> 
> Ah, but there is another approach.  It turns out that tree.h in included
> only from tree.c and tree_trace.c.  And tree_trace.c defines a CPP symbol
> RCU_TREE_NONCORE that is used elsewhere in tree.h to keep tree_trace.c's
> mitts off a number of attractive but dangerous functions.  So I just put
> the array under "#ifndef RCU_TREE_NONCORE".
> 
> Fair enough?

Fair enough.

Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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#1284683 — Re: [PATCH tip/core/rcu 6/8] rcutorture: Print symbolic name for ->gp_state

On Fri, Dec 04, 2015 at 05:04:21PM -0800, Josh Triplett wrote:
> On Fri, Dec 04, 2015 at 04:23:50PM -0800, Paul E. McKenney wrote:
> > Currently, ->gp_state is printed as an integer, which slows debugging.
> > This commit therefore prints a symbolic name in addition to the integer.
> > 
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > [ Updated to fix relational operator called out by Dan Carpenter. ]
> > ---
> >  kernel/rcu/tree.c | 15 +++++++++++++--
> >  kernel/rcu/tree.h |  9 +++++++++
> >  2 files changed, 22 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 7b78c88e19a3..491c99a73996 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -1187,6 +1187,16 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
> >  }
> >  
> >  /*
> > + * Convert a ->gp_state value to a character string.
> > + */
> > +static char *gp_state_getname(short gs)
> 
> Same comment about "const char *"

Good point, fixed!

> > +{
> > +	if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names))
> > +		return "???";
> > +	return gp_state_names[gs];
> > +}
> > +
> > +/*
> >   * Complain about starvation of grace-period kthread.
> >   */
> >  static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
> > @@ -1197,10 +1207,11 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
> >  	j = jiffies;
> >  	gpa = READ_ONCE(rsp->gp_activity);
> >  	if (j - gpa > 2 * HZ) {
> > -		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n",
> > +		pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x %s(%d) ->state=%#lx\n",
> >  		       rsp->name, j - gpa,
> >  		       rsp->gpnum, rsp->completed,
> > -		       rsp->gp_flags, rsp->gp_state,
> > +		       rsp->gp_flags,
> > +		       gp_state_getname(rsp->gp_state), rsp->gp_state,
> >  		       rsp->gp_kthread ? rsp->gp_kthread->state : ~0);
> >  		if (rsp->gp_kthread)
> >  			sched_show_task(rsp->gp_kthread);
> > diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> > index f32bebb6bc90..f0304988e3f8 100644
> > --- a/kernel/rcu/tree.h
> > +++ b/kernel/rcu/tree.h
> > @@ -544,6 +544,15 @@ struct rcu_state {
> >  #define RCU_GP_DOING_FQS 4	/* Wait done for force-quiescent-state time. */
> >  #define RCU_GP_CLEANUP   5	/* Grace-period cleanup started. */
> >  #define RCU_GP_CLEANED   6	/* Grace-period cleanup complete. */
> > +static char * const gp_state_names[] = {
> 
> Same comment about "const char * const", but also, should this really go
> in a header file?  Do any circumstances exist where this header could
> get included in more than one source file in a given build?  If so,
> multiple copies of this array could potentially end up in the binary, if
> the compiler fails to merge them.

I added the const.

However, I left the array in the .h file.  The issue is that the #defines
really have to be in the tree.h file.  Given that, if I move the array
elsewhere, they will very likely drift out of sync.  So this sounds like
a job for the compiler/linker...

Ah, but there is another approach.  It turns out that tree.h in included
only from tree.c and tree_trace.c.  And tree_trace.c defines a CPP symbol
RCU_TREE_NONCORE that is used elsewhere in tree.h to keep tree_trace.c's
mitts off a number of attractive but dangerous functions.  So I just put
the array under "#ifndef RCU_TREE_NONCORE".

Fair enough?

							Thanx, Paul

> > +	"RCU_GP_IDLE",
> > +	"RCU_GP_WAIT_GPS",
> > +	"RCU_GP_DONE_GPS",
> > +	"RCU_GP_WAIT_FQS",
> > +	"RCU_GP_DOING_FQS",
> > +	"RCU_GP_CLEANUP",
> > +	"RCU_GP_CLEANED",
> > +};
> >  
> >  extern struct list_head rcu_struct_flavors;
> >  
> > -- 
> > 2.5.2
> > 
> 

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