Re: [PATCH] ARM: oprofile: Always allow backtraces

[Robert Richter <robert.richter@amd.com>]

On 20.01.11 04:42:24, Will Deacon wrote:
> Hi Ari,
> 
> > Always allow backtrace when using oprofile on ARM, even if a PMU
> > isn't present.
> > 
> > Restores functionality originally introduced in
> > 1b7b56982fdcd9d85effd76f3928cf5d6eb26155 by Richard Purdie.
> 
> Well spotted, I'd forgotten we still want this for timer mode.
> Comments inline.
>  
> > diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
> > index 8aa9744..a23e5ae 100644
> > --- a/arch/arm/oprofile/common.c
> > +++ b/arch/arm/oprofile/common.c
> > @@ -46,6 +46,7 @@ char *op_name_from_perf_id(void)
> >  		return NULL;
> >  	}
> >  }
> > +#endif
> > 
> >  static int report_trace(struct stackframe *frame, void *d)
> >  {
> > @@ -109,6 +110,7 @@ static void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
> >  		tail = user_backtrace(tail);
> >  }
> > 
> > +#ifdef CONFIG_HW_PERF_EVENTS
> 
> Can you reorder the backtrace stuff so that we don't need the extra
> #endif/#ifdef please?

I would like to go even further, see the diff below.

-Robert

---
 arch/arm/oprofile/common.c |   45 ++++++++++++++++++++++++-------------------
 1 files changed, 25 insertions(+), 20 deletions(-)

diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
index 8aa9744..916aa2e 100644
--- a/arch/arm/oprofile/common.c
+++ b/arch/arm/oprofile/common.c
@@ -47,18 +47,6 @@ char *op_name_from_perf_id(void)
 	}
 }
 
-static int report_trace(struct stackframe *frame, void *d)
-{
-	unsigned int *depth = d;
-
-	if (*depth) {
-		oprofile_add_trace(frame->pc);
-		(*depth)--;
-	}
-
-	return *depth == 0;
-}
-
 /*
  * The registers we're interested in are at the end of the variable
  * length saved register structure. The fp points at the end of this
@@ -91,6 +79,30 @@ static struct frame_tail* user_backtrace(struct frame_tail *tail)
 	return buftail[0].fp-1;
 }
 
+#else
+
+static int oprofile_arch_init(struct oprofile_operations *ops)
+{
+	pr_info("oprofile: hardware counters not available\n");
+	return -ENODEV;
+}
+
+static void oprofile_arch_exit(void) { }
+
+#endif /* CONFIG_HW_PERF_EVENTS */
+
+static int report_trace(struct stackframe *frame, void *d)
+{
+	unsigned int *depth = d;
+
+	if (*depth) {
+		oprofile_add_trace(frame->pc);
+		(*depth)--;
+	}
+
+	return *depth == 0;
+}
+
 static void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
 {
 	struct frame_tail *tail = ((struct frame_tail *) regs->ARM_fp) - 1;
@@ -111,6 +123,7 @@ static void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
 
 int __init oprofile_arch_init(struct oprofile_operations *ops)
 {
+	/* provide backtrace support also in timer mode: */
 	ops->backtrace		= arm_backtrace;
 
 	return oprofile_perf_init(ops);
@@ -120,11 +133,3 @@ void __exit oprofile_arch_exit(void)
 {
 	oprofile_perf_exit();
 }
-#else
-int __init oprofile_arch_init(struct oprofile_operations *ops)
-{
-	pr_info("oprofile: hardware counters not available\n");
-	return -ENODEV;
-}
-void __exit oprofile_arch_exit(void) {}
-#endif /* CONFIG_HW_PERF_EVENTS */
-- 
1.7.3.4



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