[PATCH] powerpc/xmon: Add 'dt' command to dump trace buffers

[PATCH] powerpc/xmon: Add 'dt' command to dump trace buffers

[Michael Ellerman]

There is a nice interface for asking ftrace to dump all its tracing
buffers. The only down side for use in xmon is that it uses printk.
Depending on circumstances printk may not work when in xmon, but it also
may, so add a 'dt' command which dumps the ftrace buffers, and add a
note to the help to mentiont that it uses printk.

Calling this routine also disables tracing, which is problematic if you
return from xmon and expect the system to keep operating normally. So
after we do the dump turn tracing back on.

Both functions already have nop versions defined for when ftrace is not
enabled, so we don't need any extra #ifdefs.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 arch/powerpc/xmon/xmon.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 786bf01691c9..31e0d63d2442 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -10,6 +10,8 @@
  *      as published by the Free Software Foundation; either version
  *      2 of the License, or (at your option) any later version.
  */
+
+#include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/sched.h>
 #include <linux/smp.h>
@@ -201,7 +203,9 @@ Commands:\n\
   di	dump instructions\n\
   df	dump float values\n\
   dd	dump double values\n\
-  dl    dump the kernel log buffer\n"
+  dl    dump the kernel log buffer\n\
+  dt    dump the tracing buffers (uses printk)\n\
+  "
 #ifdef CONFIG_PPC64
   "\
   dp[#]	dump paca for current cpu, or cpu #\n\
@@ -2255,6 +2259,9 @@ dump(void)
 		last_cmd = "di\n";
 	} else if (c == 'l') {
 		dump_log_buf();
+	} else if (c == 't') {
+		ftrace_dump(DUMP_ALL);
+		tracing_on();
 	} else if (c == 'r') {
 		scanhex(&ndump);
 		if (ndump == 0)
-- 
2.5.0

Re: powerpc/xmon: Add 'dt' command to dump trace buffers

[Michael Ellerman]

On Fri, 2015-11-06 at 02:21:17 UTC, Michael Ellerman wrote:
> There is a nice interface for asking ftrace to dump all its tracing
> buffers. The only down side for use in xmon is that it uses printk.
> Depending on circumstances printk may not work when in xmon, but it also
> may, so add a 'dt' command which dumps the ftrace buffers, and add a
> note to the help to mentiont that it uses printk.
> 
> Calling this routine also disables tracing, which is problematic if you
> return from xmon and expect the system to keep operating normally. So
> after we do the dump turn tracing back on.
> 
> Both functions already have nop versions defined for when ftrace is not
> enabled, so we don't need any extra #ifdefs.
> 
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Applied to powerpc next.

https://git.kernel.org/powerpc/c/56144ec7c93f6f18aa878560074633

cheers