Re: [PATCH] hazptr: handle NULL address in hazptr_detach

[Bradley Morgan]

On 8 September 2026 16:29:31 BST, Mathieu Desnoyers
<mathieu.desnoyers@xxxxxxxxxxxx> wrote:
>On 2026-09-08 11:24, Bradley Morgan wrote:
>> On 8 September 2026 16:22:14 BST, Mathieu Desnoyers
>> <mathieu.desnoyers@xxxxxxxxxxxx> wrote:
>>> When hazptr_acquire loads a NULL pointer, it sets:
>>> 
>>> - slot_item->slot.addr = NULL,
>>> - slot_item->ctx.ctx = ctx
>>> - ctx->slot = slot
>>> 
>>> And it returns NULL.
>>> 
>>> Then hazptr_detach is called on this ctx, it will act on the ctx as if
>>> needed to be promoted to backup slot, even though it has a NULL addr.
>>> 
>>> Looking at what hazptr_note_context_switch() does before promoting
>>> to backup slot, it checks for a NULL slot->addr, which is exactly
>>> what is missing from hazptr_detach.
>>> 
>>> With this in place there would be no need to explicitly check the
>>> hazptr_acquire() return value before calling hazptr_detach().
>>> 
>>> hazptr_release() has a early return check for NULL addr as well, so it
>>> makes sense that detach does an early return (no-op) similarly.
>>> 
>> 
>> You shall kill me for this!!
>> 
>> Could you perhaps do a splat in ze commit description pls?
>
>The splat is available at the "Closes" URL below. I'm not sure whether
>we should duplicate this verbose information ?
>
>Paul ?
>


This is a example of what I did.