On Thu, Aug 15, 2024 at 8:58 PM Jann Horn <jannh@xxxxxxxxxx> wrote: > Stupid question: Is this uprobe stuff actually such a hot codepath > that it makes sense to optimize it to be faster than the page fault > path? > That's what I implicitly asked, hoping a down_read on vma would do it, but Andrii claims multiple parallel lookups on the same vma are a problem. Even so, I suspect something *simple* is doable here which avoids any writes to vmas and does not need the mm-wide sequence counter. It may be requirements are lax enough that merely observing some state is the same before and after uprobe lookup will be sufficient, or maybe some other hackery is viable without messing with fences in vma_start_write. -- Mateusz Guzik <mjguzik gmail.com>
