On Mon, 2005-01-17 at 13:11 +0100, Guillaume Thouvenin wrote:
> +/*
> + * fork_hook is a pointer to a function to call when forking if it
> + * isn't NULL.
> + */
> +void (*fork_hook) (int, int) = NULL;
I added a lock to protect the global pointer "fork_hook".
spinlock_t fork_hook_lock = SPIN_LOCK_UNLOCKED;
I removed the identifier fork_hook_id and here is the new code for the
fork_hook:
/**
* trace_fork: call a given external function when forking
* @func: function to call
*
* This function sets the fork_hook and makes some sanity checks.
* Function returns 0 on success, -1 on failure (ie hook is
* already used).
* Limitation: currently, it can be used by only one module
*/
int trace_fork(void (*func) (int, int))
{
int err = 0;
spin_lock(&fork_hook_lock);
/* We can set the hook if it's not already used */
if (func != NULL) {
if (fork_hook == NULL)
fork_hook = func;
else
err = -EBUSY;
} else
/* no check when releasing */
fork_hook = NULL;
spin_unlock(&fork_hook_lock);
/* Request can not be satisfied */
return err;
}
EXPORT_SYMBOL(trace_fork);
It implies a very small modification in relay_fork.c
> --------8< relay_fork.c module ----------------------
> /**
> * rfd_init -
> */
> static int __init rfd_init(void)
> {
> int retval;
>
> retval = trace_fork(&rfd_relay_fork_info, TRACE_FORK_ID);
retval = trace_fork(&rfd_relay_fork_info);
...
> }
>
> /**
> * rfd_cleanup -
> */
> static void __exit rfd_cleanup(void)
> {
> struct list_head *pos; /* use as a loop counter */
> struct list_head *next; /* temporary storage */
> trace_fork(NULL, TRACE_FORK_ID);
/* don't forget to release the fork hook */
trace_fork(NULL);
...
> }
Any comments are welcome
Guillaume
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