On 2023-06-23 19:36:55 [+0900], Tetsuo Handa wrote: > /* > * Zonelists may change due to hotplug during allocation. Detect when zonelists > * have been rebuilt so allocation retries. Reader side does not lock and > * retries the allocation if zonelist changes. Writer side is protected by the > * embedded spin_lock. > */ > > is not accurate. Something like below? > > If !RT, reader side does not lock and retries the allocation if zonelist changes. > If RT, reader side grabs and releases the embedded spin_lock in order to wait > for zonelist change operations to complete. I wouldn't sprinkle it around the code. It is implementation specific for PREEMPT_RT and documentation wise it would belong to Documentation/locking/seqlock.rst I don't think extra knowledge benefits the code. If this piece if information is needed I would suggest to include it to the original documentation for seqlock. > Hmm, I feel worried that kmalloc(GFP_ATOMIC) from hard IRQ context > might sleep if RT... Relax and don't worry. PREEMPT_RT does not allow (or has afaik) memory allocations from hard IRQ context (or preempt-disable sections). Sebastian
