diff mbox series

[v2,1/3] tracing: Replace TRACE_FLAG_IRQS_NOSUPPORT with its config option.

Message ID 20241021151257.102296-2-bigeasy@linutronix.de (mailing list archive)
State New
Headers show
Series Lazy preemption leftovers | expand

Commit Message

Sebastian Andrzej Siewior Oct. 21, 2024, 3:08 p.m. UTC 
From: Thomas Gleixner <tglx@linutronix.de>

The TRACE_FLAG_IRQS_NOSUPPORT flag is used by tracing_gen_ctx.*() to
signal that CONFIG_TRACE_IRQFLAGS_SUPPORT is not enabled and tracing IRQ
flags is not supported.

This could be replaced by using the 0 as flags and then deducting that
there is no IRQFLAGS_SUPPORT based on the config option. The downside is
that without CONFIG_TRACE_IRQFLAGS_SUPPORT we can not distinguish
between no-IRQ passed flags and callers which passed 0. On the upside we
have room for one additional flags which could be used for LAZY_PREEMPTION.

Remove TRACE_FLAG_IRQS_NOSUPPORT and set it flags are 0 and
CONFIG_TRACE_IRQFLAGS_SUPPORT is not set.

[bigeasy: Commit descrption.]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/linux/trace_events.h |    7 +++----
 kernel/trace/trace_output.c  |    2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

Comments

Steven Rostedt Oct. 22, 2024, 7:14 a.m. UTC | #1 
On Mon, 21 Oct 2024 17:08:40 +0200
Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

> From: Thomas Gleixner <tglx@linutronix.de>
> 
> The TRACE_FLAG_IRQS_NOSUPPORT flag is used by tracing_gen_ctx.*() to
> signal that CONFIG_TRACE_IRQFLAGS_SUPPORT is not enabled and tracing IRQ
> flags is not supported.
> 
> This could be replaced by using the 0 as flags and then deducting that
> there is no IRQFLAGS_SUPPORT based on the config option. The downside is
> that without CONFIG_TRACE_IRQFLAGS_SUPPORT we can not distinguish
> between no-IRQ passed flags and callers which passed 0. On the upside we
> have room for one additional flags which could be used for LAZY_PREEMPTION.
> 
> Remove TRACE_FLAG_IRQS_NOSUPPORT and set it flags are 0 and
> CONFIG_TRACE_IRQFLAGS_SUPPORT is not set.

We could also add that we have:

#
# Minimum requirements an architecture has to meet for us to
# be able to offer generic tracing facilities:
#
config TRACING_SUPPORT
        bool
        depends on TRACE_IRQFLAGS_SUPPORT
        depends on STACKTRACE_SUPPORT
        default y

So this can't even be built without TRACE_IRQFLAGS_SUPPORT!

> 
> [bigeasy: Commit descrption.]
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  include/linux/trace_events.h |    7 +++----
>  kernel/trace/trace_output.c  |    2 +-
>  2 files changed, 4 insertions(+), 5 deletions(-)
> 
> --- a/include/linux/trace_events.h
> +++ b/include/linux/trace_events.h
> @@ -184,8 +184,7 @@ unsigned int tracing_gen_ctx_irq_test(un
>  
>  enum trace_flag_type {
>  	TRACE_FLAG_IRQS_OFF		= 0x01,
> -	TRACE_FLAG_IRQS_NOSUPPORT	= 0x02,
> -	TRACE_FLAG_NEED_RESCHED		= 0x04,
> +	TRACE_FLAG_NEED_RESCHED		= 0x02,

These flags are user visible (I probably should move them into uapi).
They are parsed by libtraceevent.

Please just remove NOSUPPORT and do not touch NEED_RESCHED.


>  	TRACE_FLAG_HARDIRQ		= 0x08,
>  	TRACE_FLAG_SOFTIRQ		= 0x10,
>  	TRACE_FLAG_PREEMPT_RESCHED	= 0x20,
> @@ -211,11 +210,11 @@ static inline unsigned int tracing_gen_c
>  
>  static inline unsigned int tracing_gen_ctx_flags(unsigned long irqflags)
>  {
> -	return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT);
> +	return tracing_gen_ctx_irq_test(0);
>  }
>  static inline unsigned int tracing_gen_ctx(void)
>  {
> -	return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT);
> +	return tracing_gen_ctx_irq_test(0);
>  }
>  #endif
>  
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -460,7 +460,7 @@ int trace_print_lat_fmt(struct trace_seq
>  		(entry->flags & TRACE_FLAG_IRQS_OFF && bh_off) ? 'D' :
>  		(entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' :
>  		bh_off ? 'b' :
> -		(entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' :
> +		!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_SUPPORT) ? 'X' :

Probably can even remove this check.

-- Steve

>  		'.';
>  
>  	switch (entry->flags & (TRACE_FLAG_NEED_RESCHED |
Sebastian Andrzej Siewior Oct. 22, 2024, 9:52 a.m. UTC | #2 
On 2024-10-22 03:14:18 [-0400], Steven Rostedt wrote:
> On Mon, 21 Oct 2024 17:08:40 +0200
> Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> 
> > From: Thomas Gleixner <tglx@linutronix.de>
> > 
> > The TRACE_FLAG_IRQS_NOSUPPORT flag is used by tracing_gen_ctx.*() to
> > signal that CONFIG_TRACE_IRQFLAGS_SUPPORT is not enabled and tracing IRQ
> > flags is not supported.
> > 
> > This could be replaced by using the 0 as flags and then deducting that
> > there is no IRQFLAGS_SUPPORT based on the config option. The downside is
> > that without CONFIG_TRACE_IRQFLAGS_SUPPORT we can not distinguish
> > between no-IRQ passed flags and callers which passed 0. On the upside we
> > have room for one additional flags which could be used for LAZY_PREEMPTION.
> > 
> > Remove TRACE_FLAG_IRQS_NOSUPPORT and set it flags are 0 and
> > CONFIG_TRACE_IRQFLAGS_SUPPORT is not set.
> 
> We could also add that we have:
> 
> #
> # Minimum requirements an architecture has to meet for us to
> # be able to offer generic tracing facilities:
> #
> config TRACING_SUPPORT
>         bool
>         depends on TRACE_IRQFLAGS_SUPPORT
>         depends on STACKTRACE_SUPPORT
>         default y
> 
> So this can't even be built without TRACE_IRQFLAGS_SUPPORT!

Good point. So we could TRACE_FLAG_IRQS_NOSUPPORT since it can't be
used. This is since commit 0ea5ee035133a ("tracing: Remove PPC32 wart
from config TRACING_SUPPORT").

> > +++ b/include/linux/trace_events.h
> > @@ -184,8 +184,7 @@ unsigned int tracing_gen_ctx_irq_test(un
> >  
> >  enum trace_flag_type {
> >  	TRACE_FLAG_IRQS_OFF		= 0x01,
> > -	TRACE_FLAG_IRQS_NOSUPPORT	= 0x02,
> > -	TRACE_FLAG_NEED_RESCHED		= 0x04,
> > +	TRACE_FLAG_NEED_RESCHED		= 0x02,
> 
> These flags are user visible (I probably should move them into uapi).
> They are parsed by libtraceevent.
> 
> Please just remove NOSUPPORT and do not touch NEED_RESCHED.

Then I put the lazy bit where we have not NOSUPPORT.

> >  	TRACE_FLAG_HARDIRQ		= 0x08,
> >  	TRACE_FLAG_SOFTIRQ		= 0x10,
> >  	TRACE_FLAG_PREEMPT_RESCHED	= 0x20,
> > --- a/kernel/trace/trace_output.c
> > +++ b/kernel/trace/trace_output.c
> > @@ -460,7 +460,7 @@ int trace_print_lat_fmt(struct trace_seq
> >  		(entry->flags & TRACE_FLAG_IRQS_OFF && bh_off) ? 'D' :
> >  		(entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' :
> >  		bh_off ? 'b' :
> > -		(entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' :
> > +		!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_SUPPORT) ? 'X' :
> 
> Probably can even remove this check.

Yes.

> -- Steve

Sebastian
Steven Rostedt Oct. 22, 2024, 10:19 a.m. UTC | #3 
On Tue, 22 Oct 2024 11:52:41 +0200
Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

> > 
> > Please just remove NOSUPPORT and do not touch NEED_RESCHED.  
> 
> Then I put the lazy bit where we have not NOSUPPORT.

I'm afraid user space will confuse this with the NOSUPPORT.

-- Steve
Sebastian Andrzej Siewior Oct. 22, 2024, 10:29 a.m. UTC | #4 
On 2024-10-22 06:19:59 [-0400], Steven Rostedt wrote:
> On Tue, 22 Oct 2024 11:52:41 +0200
> Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> 
> > > 
> > > Please just remove NOSUPPORT and do not touch NEED_RESCHED.  
> > 
> > Then I put the lazy bit where we have not NOSUPPORT.
> 
> I'm afraid user space will confuse this with the NOSUPPORT.

So? We don't ignore this for now and recycle that bit? If I got it
right, only PPC32 was using that NOSUPPORT bit.
What are the options given that it has to be an 8 bit field?

> -- Steve

Sebastian
diff mbox series

Patch

--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -184,8 +184,7 @@  unsigned int tracing_gen_ctx_irq_test(un
 
 enum trace_flag_type {
 	TRACE_FLAG_IRQS_OFF		= 0x01,
-	TRACE_FLAG_IRQS_NOSUPPORT	= 0x02,
-	TRACE_FLAG_NEED_RESCHED		= 0x04,
+	TRACE_FLAG_NEED_RESCHED		= 0x02,
 	TRACE_FLAG_HARDIRQ		= 0x08,
 	TRACE_FLAG_SOFTIRQ		= 0x10,
 	TRACE_FLAG_PREEMPT_RESCHED	= 0x20,
@@ -211,11 +210,11 @@  static inline unsigned int tracing_gen_c
 
 static inline unsigned int tracing_gen_ctx_flags(unsigned long irqflags)
 {
-	return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT);
+	return tracing_gen_ctx_irq_test(0);
 }
 static inline unsigned int tracing_gen_ctx(void)
 {
-	return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT);
+	return tracing_gen_ctx_irq_test(0);
 }
 #endif
 
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -460,7 +460,7 @@  int trace_print_lat_fmt(struct trace_seq
 		(entry->flags & TRACE_FLAG_IRQS_OFF && bh_off) ? 'D' :
 		(entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' :
 		bh_off ? 'b' :
-		(entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' :
+		!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_SUPPORT) ? 'X' :
 		'.';
 
 	switch (entry->flags & (TRACE_FLAG_NEED_RESCHED |