On Thu, Aug 26, 2021 at 04:50:28PM +0000, Michael Kelley wrote: > From: Long Li <longli@xxxxxxxxxxxxx> Sent: Wednesday, August 25, 2021 1:25 PM > > > > > > > I thought list_for_each_entry_safe() is for use when list manipulation is *not* > > > protected by a lock and you want to safely walk the list even if an entry gets > > > removed. If the list is protected by a lock or not subject to contention (as is the > > > case here), then > > > list_for_each_entry() is the simpler implementation. The original > > > implementation didn't need to use the _safe version because of the spin lock. > > > > > > Or do I have it backwards? > > > > > > Michael > > > > I think we need list_for_each_entry_safe() because we delete the list elements while going through them: > > > > Here is the comment on list_for_each_entry_safe(): > > /** > > * Loop through the list, keeping a backup pointer to the element. This > > * macro allows for the deletion of a list element while looping through the > > * list. > > * > > * See list_for_each_entry for more details. > > */ > > > > Got it. Thanks (and to Rob Herring). I read that comment but > with the wrong assumptions and didn't understand it correctly. > > Interestingly, pci-hyperv.c has another case of looping through > this list and removing items where the _safe version is not used. > See pci_devices_present_work() where the missing children are > moved to a list on the stack. That can be converted too, I think. The original code is not wrong per-se. It is just not as concise as using list_for_each_entry_safe. Wei. > > Michael
