Hi Steve, I found out that the tracer got stuck on ppc32 platforms because some early functions call _mcount before mcount_enabled is initialized at all. I made a patch, which marks these functions as notrace to solve this problem. With this patch I can successfully boot up our mpc5200b platform and make latency trace. (tested with -b switch in cyclictest). Please comment. I made my patch against the -rt2 tree since the dummy call early_printk() in -rt3 conflicts with our implementation of a functional early_printk(). It should also work with -rt3 though. cheers Luotao Fu -- Dipl.-Ing. Luotao Fu | Phone: +49-5121-206917-3 Pengutronix - Linux Solutions for Science and Industry Entwicklungszentrum Nord http://www.pengutronix.de
Subject: don't trace early init functions for ppc32
By: Luotao Fu <l.fu@xxxxxxxxxxxxxx>
If the latency tracer is turned on in the kernel config, _mcount calls are
added automatically to every function call during compiling since -pg
compiling flag is set. _mcount() checks first the variable mcount_enabled.
(see implementation of _mcount() in arch/powerpc/kernel/entry_32.S) This will
stuck forever if _mcount is called before mcount_enabled is initialized. Hence
we mark some init functions as notrace, so that _mcount calls are not added to
these functions.
Signed-off-by: Luotao Fu <l.fu@xxxxxxxxxxxxxx>
---
arch/powerpc/kernel/cputable.c | 4 ++--
arch/powerpc/kernel/io.c | 2 +-
arch/powerpc/kernel/setup_32.c | 2 +-
3 files changed, 4 insertions(+), 4 deletions(-)
Index: arch/powerpc/kernel/cputable.c
===================================================================
--- arch/powerpc/kernel/cputable.c.orig
+++ arch/powerpc/kernel/cputable.c
@@ -1333,7 +1333,7 @@ static struct cpu_spec __initdata cpu_sp
static struct cpu_spec the_cpu_spec;
-struct cpu_spec * __init identify_cpu(unsigned long offset, unsigned int pvr)
+notrace struct cpu_spec * __init identify_cpu(unsigned long offset, unsigned int pvr)
{
struct cpu_spec *s = cpu_specs;
struct cpu_spec *t = &the_cpu_spec;
@@ -1380,7 +1380,7 @@ struct cpu_spec * __init identify_cpu(un
return NULL;
}
-void do_feature_fixups(unsigned long value, void *fixup_start, void *fixup_end)
+notrace void do_feature_fixups(unsigned long value, void *fixup_start, void *fixup_end)
{
struct fixup_entry {
unsigned long mask;
Index: arch/powerpc/kernel/io.c
===================================================================
--- arch/powerpc/kernel/io.c.orig
+++ arch/powerpc/kernel/io.c
@@ -120,7 +120,7 @@ EXPORT_SYMBOL(_outsl_ns);
#define IO_CHECK_ALIGN(v,a) ((((unsigned long)(v)) & ((a) - 1)) == 0)
-void _memset_io(volatile void __iomem *addr, int c, unsigned long n)
+notrace void _memset_io(volatile void __iomem *addr, int c, unsigned long n)
{
void *p = (void __force *)addr;
u32 lc = c;
Index: arch/powerpc/kernel/setup_32.c
===================================================================
--- arch/powerpc/kernel/setup_32.c.orig
+++ arch/powerpc/kernel/setup_32.c
@@ -88,7 +88,7 @@ int ucache_bsize;
* from the address that it was linked at, so we must use RELOC/PTRRELOC
* to access static data (including strings). -- paulus
*/
-unsigned long __init early_init(unsigned long dt_ptr)
+notrace unsigned long __init early_init(unsigned long dt_ptr)
{
unsigned long offset = reloc_offset();
struct cpu_spec *spec;
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