vanishing ioctl handler debugging
We've had several reoprts of the CPU jumping to 0x00000000 is do_ioctl(). I
assume that there's a race and someone is zeroing out the ioctl handler while
this CPU waits for the lock_kernel().
The patch adds code to detect this, then emits stuff which will hopefuly lead
us to the culprit.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 479c103..8c90cbc 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -12,6 +12,7 @@
#include <linux/fs.h>
#include <linux/security.h>
#include <linux/module.h>
+#include <linux/kallsyms.h>
#include <asm/uaccess.h>
#include <asm/ioctls.h>
@@ -20,6 +21,7 @@
unsigned long arg)
{
int error = -ENOTTY;
+ void *f;
if (!filp->f_op)
goto out;
@@ -29,10 +31,16 @@
if (error == -ENOIOCTLCMD)
error = -EINVAL;
goto out;
- } else if (filp->f_op->ioctl) {
+ } else if ((f = filp->f_op->ioctl)) {
lock_kernel();
- error = filp->f_op->ioctl(filp->f_path.dentry->d_inode,
- filp, cmd, arg);
+ if (!filp->f_op->ioctl) {
+ printk("%s: ioctl %p disappeared\n", __FUNCTION__, f);
+ print_symbol("symbol: %s\n", (unsigned long)f);
+ dump_stack();
+ } else {
+ error = filp->f_op->ioctl(filp->f_path.dentry->d_inode,
+ filp, cmd, arg);
+ }
unlock_kernel();
}
