Re: [PATCH v2 0/2] Lock and Pointer guards

From: Peter Zijlstra
Date: Tue May 30 2023 - 05:35:20 EST

On Tue, May 30, 2023 at 11:23:42AM +0200, Peter Zijlstra wrote:

> Yes, it's a wee bit more involved, but I'm thinking it gives a fair
> amount of flexibility and we don't need to ret rid of
> -Wdeclaration-after-statement.

One other thing I forgot to point put; it allows things like:

int store_fd(int fd)
ptr_guard(fdput, f) = fdget(fd);
void *ret;
if (!f.file)
return -EBADF;
ret = xa_store(&xarray, f.file->private, f);
if (xa_is_err(ret))
return xa_err(ret);
f = null_ptr(fdput); // xarray now owns f
return 0;

Where we can assign null_ptr() to clear the guard and inhibit the
cleanup function to pass ownership around.