Hi Kemeng,
On Mon, Aug 21, 2023 at 6:27 PM Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx> wrote:
> >
> Agreed. We assume pcp->count is protected by pcp->lock. Instead of make code
> work in case pcp->count could be changed without lock held, it's more reasonble
> to modify pcp->count with pcp->lock held in BPF program.
The lock is holded when pcp->count is modified. It is going through
the kernel page
allocation API. The issue is nest memory allocation inside spin_lock()
introduced by BPF.
The execution sequence is like this:
count = min(pcp->count, count);
/* Ensure requested pindex is drained first. */
pindex = pindex - 1;
bpf_injected_spin_lock_irqsave {
alloc_page();
original spin_lock_irqsave(&zone->lock, flags) ;
}
Chris
Chris
