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vanishing ioctl handler debugging

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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>
This commit is contained in:
Andrew Morton 2007-06-03 13:50:41 -07:00 committed by Linus Torvalds
parent 4c738480d2
commit 78ae87c3cd
1 changed files with 11 additions and 3 deletions
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10
fs/ioctl.c
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@ -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 @@ static long do_ioctl(struct file *filp, unsigned int cmd,
unsigned long arg)
{
int error = -ENOTTY;
void *f;
if (!filp->f_op)
goto out;
@ -29,10 +31,16 @@ static long do_ioctl(struct file *filp, unsigned int cmd,
if (error == -ENOIOCTLCMD)
error = -EINVAL;
goto out;
} else if (filp->f_op->ioctl) {
} else if ((f = filp->f_op->ioctl)) {
lock_kernel();
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();
}