On Fri, May 03, 2024 at 02:42:22PM -0700, Linus Torvalds wrote: > On Fri, 3 May 2024 at 14:36, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > ... the last part is no-go - poll_wait() must be able to grab a reference > > (well, the callback in it must) > > Yeah. I really think that *poll* itself is doing everything right. It > knows that it's called with a file pointer with a reference, and it > adds its own references as needed. Not really. Note that select's __pollwait() does *NOT* leave a reference at the mercy of driver - it's stuck into poll_table_entry->filp and the poll_freewait() knows how to take those out. dmabuf does something very different - it grabs the damn thing into its private data structures and for all we know it could keep it for a few hours, until some even materializes.
