On 11/18/2013 10:46 AM, Meelis Roos wrote:
First I compared the configurations of working and nonworking machines
(there were 2 different machines from the same era with problem), then
did some conf bisecting and found that CONFIG_SUN_OPENPROMFS causes the
RED problem in 3.12-rc5 when compiled modular and module loaded. It did
not happen when it was compiled statically, or modular but module was
not loaded. Reduced minimalistic configuration that causes this on Ultra
5 is attached to this mail.
Is the problem unique to these 2 machines given this configuration, or is
the problem reproduceable on other machines using this configuration?
With the minimalistic conf, I redid the bisect with a different range
end, fixing vmalloc.h include when needed. This led me into tty changes
again, maybe more precise this time because of vmalloc fixes (no commits
skipped this time). This is the culprit today:
20bafb3d23d108bc0a896eb8b7c1501f4f649b77 is the first bad commit
commit 20bafb3d23d108bc0a896eb8b7c1501f4f649b77
Author: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Date: Sat Jun 15 10:21:19 2013 -0400
n_tty: Move buffers into n_tty_data
Reduce pointer reloading and improve locality-of-reference;
allocate read_buf and echo_buf within struct n_tty_data.
Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
:040000 040000 96d92e4e242c4b2ff11b25c005bccd093865b350
2822d87b2425c3e7adc7b722a20d739c9d4a3046 M drivers
This patch seems to switch ldata with its read_buf and echo_buf from
kmalloc/kfree to vmalloc/vfree (the bufs are now inlined in ldata, not
separately allocated).
Yep, this makes more sense than the original bisect.
More fields in ldata are now explicitly initialized to zero instead of
kzalloc doing it before. However, I do not see the initialization of
some of the fields - maybe they are done later in the code? I noticed
process_char_map, raw, real_raw, icanon, read_buf, echo_buf that were
zeroed before but I did not find explicit zeroing of them after the
patch. However, just adding a memset to zero ldata after vmalloc does
not change anything.
Openpromfs does not seem to be changed after 3.11 and it does not seem
to use any tty layer functions.
I still have no idea how it would interact.
Me neither. But it looks like something depends on tty working before
the mmu is initialized. David, would you know what that is?
It happens on the shutdown part of reboot, not startup - when we call
prom "boot" command, it should output "Resetting ..." and reset but
never outputs anything, then RED state exeption occurs. To the best of
my understanding, Linux does not output anything any more at that point,
only prom. Have we hooked into prom somehow? Openpromfs itselt just
seems to read the in-memory data structures of device tree.
Another strange symptom is that the problem did not happen when
openpromfs is compiled in statically, not loaded as module. When loaded
as module, its memory is vmalloc()ed... but that's probably too weak
connection to conclude anything.
What happens with the not-even-compile-tested debug patch below?
--->%---
Subject: [PATCH] Debug instrumentation of exit_openprom_fs()
Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
fs/openpromfs/inode.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/fs/openpromfs/inode.c b/fs/openpromfs/inode.c
index 8c0ceb8..9fc4c86 100644
--- a/fs/openpromfs/inode.c
+++ b/fs/openpromfs/inode.c
@@ -12,12 +12,15 @@
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/magic.h>
+#include <linux/printk.h>
#include <asm/openprom.h>
#include <asm/oplib.h>
#include <asm/prom.h>
#include <asm/uaccess.h>
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
static DEFINE_MUTEX(op_mutex);
#define OPENPROM_ROOT_INO 0
@@ -456,6 +459,8 @@ static int __init init_openprom_fs(void)
static void __exit exit_openprom_fs(void)
{
+ pr_info("exiting\n");
+
unregister_filesystem(&openprom_fs_type);
/*
* Make sure all delayed rcu free inodes are flushed before we
@@ -463,6 +468,8 @@ static void __exit exit_openprom_fs(void)
*/
rcu_barrier();
kmem_cache_destroy(op_inode_cachep);
+
+ pr_info("exited\n");
}
module_init(init_openprom_fs)
--
1.8.1.2
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