> +static int ipath_sma_open(struct inode *in, struct file *fp)
> +{
> + int s;
> +
> + if (ipath_sma_alive) {
> + ipath_dbg("SMA already running (pid %u), failing\n",
> + ipath_sma_alive);
> + return -EBUSY;
> + }
> +
> + for (s = 0; s < atomic_read(&ipath_max); s++) {
> + struct ipath_devdata *dd = ipath_lookup(s);
> + /* we need at least one infinipath device to be initialized. */
> + if (dd && dd->ipath_flags & IPATH_INITTED) {
> + ipath_sma_alive = current->pid;
It seems there's a window here where two processes can both pass the
if (ipath_sma_alive) test and then proceed to step on each other.
- R.
On Thu, 2006-03-09 at 15:24 -0800, Roland Dreier wrote:
> It seems there's a window here where two processes can both pass the
> if (ipath_sma_alive) test and then proceed to step on each other.
Yep, this is a real race, albeit incredibly unlikely. I just turned
ipath_sma_alive into an atomic_t, and wrapped the open/close code in
spinlocks.
<b
Bryan> Yep, this is a real race, albeit incredibly unlikely. I
Bryan> just turned ipath_sma_alive into an atomic_t, and wrapped
Bryan> the open/close code in spinlocks.
How does making it an atomic_t help? I think you're only going to be
using atomic_set() and atomic_read(), and atomic_t doesn't provide
anything in that case.
- R.