[PATCH] powerpc: Add doorbell tracepoints

When analysing sources of OS jitter, I noticed that doorbells cannot be
traced.

Signed-off-by: Anton Blanchard <redacted>
---
 arch/powerpc/include/asm/trace.h | 16 ++++++++++++++++
 arch/powerpc/kernel/dbell.c      |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/arch/powerpc/include/asm/trace.h b/arch/powerpc/include/asm/trace.h
index d018e8602694..eb9aa0f1561e 100644
--- a/arch/powerpc/include/asm/trace.h
+++ b/arch/powerpc/include/asm/trace.h

@@ -54,6 +54,22 @@ DEFINE_EVENT(ppc64_interrupt_class, timer_interrupt_exit,
 	TP_ARGS(regs)
 );
 
+#ifdef CONFIG_PPC_DOORBELL
+DEFINE_EVENT(ppc64_interrupt_class, doorbell_exception_entry,
+
+	TP_PROTO(struct pt_regs *regs),
+
+	TP_ARGS(regs)
+);
+
+DEFINE_EVENT(ppc64_interrupt_class, doorbell_exception_exit,
+
+	TP_PROTO(struct pt_regs *regs),
+
+	TP_ARGS(regs)
+);
+#endif
+
 #ifdef CONFIG_PPC_PSERIES
 extern int hcall_tracepoint_regfunc(void);
 extern void hcall_tracepoint_unregfunc(void);

diff --git a/arch/powerpc/kernel/dbell.c b/arch/powerpc/kernel/dbell.c
index b6fe883b1016..5ec3b3835925 100644
--- a/arch/powerpc/kernel/dbell.c
+++ b/arch/powerpc/kernel/dbell.c

@@ -18,6 +18,7 @@
 #include <asm/dbell.h>
 #include <asm/irq_regs.h>
 #include <asm/kvm_ppc.h>
+#include <asm/trace.h>
 
 #ifdef CONFIG_SMP
 

@@ -81,6 +82,7 @@ void doorbell_exception(struct pt_regs *regs)
 	struct pt_regs *old_regs = set_irq_regs(regs);
 
 	irq_enter();
+	trace_doorbell_entry(regs);
 
 	ppc_msgsync();
 

@@ -91,6 +93,7 @@ void doorbell_exception(struct pt_regs *regs)
 
 	smp_ipi_demux_relaxed(); /* already performed the barrier */
 
+	trace_doorbell_exit(regs);
 	irq_exit();
 	set_irq_regs(old_regs);
 }

-- 
2.17.1

On Wed,  3 Oct 2018 10:29:57 +1000
Anton Blanchard [off-list ref] wrote:

When analysing sources of OS jitter, I noticed that doorbells cannot be
traced.

Signed-off-by: Anton Blanchard <redacted>

Acked-by: Nicholas Piggin <npiggin@gmail.com>

On Wed, 2018-10-03 at 10:29 +1000, Anton Blanchard wrote:

When analysing sources of OS jitter, I noticed that doorbells cannot be
traced.

Signed-off-by: Anton Blanchard <redacted>

Hi Anton,

snowpatch builds failed for this patch on all 64-bit configurations (ppc64e, ppc64
and ppc64le) with the following:

arch/powerpc/kernel/dbell.c:85:9: error: undefined identifier
'trace_doorbell_entry'
arch/powerpc/kernel/dbell.c:96:9: error: undefined identifier
'trace_doorbell_exit'
./arch/powerpc/include/asm/spinlock.h:171:9: warning: context imbalance in
'key_user_put' - unexpected unlock
arch/powerpc/kernel/dbell.c: In function 'doorbell_exception':
arch/powerpc/kernel/dbell.c:85:2: error: implicit declaration of function
'trace_doorbell_entry'; did you mean 'trace_irq_entry'? [-Werror=implicit-
function-declaration]
  trace_doorbell_entry(regs);
  ^~~~~~~~~~~~~~~~~~~~
  trace_irq_entry
arch/powerpc/kernel/dbell.c:96:2: error: implicit declaration of function
'trace_doorbell_exit'; did you mean 'trace_irq_exit'? [-Werror=implicit-function-
declaration]
  trace_doorbell_exit(regs);
  ^~~~~~~~~~~~~~~~~~~
  trace_irq_exit
cc1: all warnings being treated as errors
scripts/Makefile.build:305: recipe for target 'arch/powerpc/kernel/dbell.o' failed
make[1]: *** [arch/powerpc/kernel/dbell.o] Error 1
Makefile:1060: recipe for target 'arch/powerpc/kernel' failed

So does something else need to check for CONFIG_PPC_DOORBELL maybe?

You can see the failures here: http://patchwork.ozlabs.org/patch/978088/ - output
in build_new.log (I know it's not pretty in there yet, you can search for "Error
1" to find the build failure)

- Russell

Hi Russell,

snowpatch builds failed for this patch on all 64-bit configurations
(ppc64e, ppc64 and ppc64le) with the following:

Thanks! Stupid bug on my part, need more quilt ref. Update to follow.

Anton

arch/powerpc/kernel/dbell.c:85:9: error: undefined identifier
'trace_doorbell_entry'
arch/powerpc/kernel/dbell.c:96:9: error: undefined identifier
'trace_doorbell_exit'
./arch/powerpc/include/asm/spinlock.h:171:9: warning: context
imbalance in 'key_user_put' - unexpected unlock
arch/powerpc/kernel/dbell.c: In function 'doorbell_exception':
arch/powerpc/kernel/dbell.c:85:2: error: implicit declaration of
function 'trace_doorbell_entry'; did you mean 'trace_irq_entry'?
[-Werror=implicit- function-declaration]
  trace_doorbell_entry(regs);
  ^~~~~~~~~~~~~~~~~~~~
  trace_irq_entry
arch/powerpc/kernel/dbell.c:96:2: error: implicit declaration of
function 'trace_doorbell_exit'; did you mean 'trace_irq_exit'?
[-Werror=implicit-function- declaration]
  trace_doorbell_exit(regs);
  ^~~~~~~~~~~~~~~~~~~
  trace_irq_exit
cc1: all warnings being treated as errors
scripts/Makefile.build:305: recipe for target
'arch/powerpc/kernel/dbell.o' failed make[1]: ***
[arch/powerpc/kernel/dbell.o] Error 1 Makefile:1060: recipe for
target 'arch/powerpc/kernel' failed

So does something else need to check for CONFIG_PPC_DOORBELL maybe?

You can see the failures here:
http://patchwork.ozlabs.org/patch/978088/ - output in build_new.log
(I know it's not pretty in there yet, you can search for "Error 1" to
find the build failure)

- Russell