linux-kernel - Re: [PATCH RFC v2 06/20] slab: make percpu sheaves compatible with kmalloc_nolock()/kfree

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Message-ID: <20260114150747.ziWhVVQM@linutronix.de>
Date: Wed, 14 Jan 2026 16:07:47 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Harry Yoo <harry.yoo@...cle.com>, Petr Tesarik <ptesarik@...e.com>,
	Christoph Lameter <cl@...two.org>,
	David Rientjes <rientjes@...gle.com>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Hao Li <hao.li@...ux.dev>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Uladzislau Rezki <urezki@...il.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Alexei Starovoitov <ast@...nel.org>, linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-rt-devel@...ts.linux.dev,
	bpf <bpf@...r.kernel.org>, kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [PATCH RFC v2 06/20] slab: make percpu sheaves compatible with
 kmalloc_nolock()/kfree_nolock()

On 2026-01-14 15:05:34 [+0100], Vlastimil Babka wrote:
> > Yes IIRC Hao Li pointed that out before. We'll be able to remove that
> > !preemptible() check that we area about to add by the patch above.
> > 
> > But I'm not sure we can remove (or "not put back") the "in_nmi() ||
> > in_hardirq()" too, because as you said it was added with different reasoning
> > initially?
> 
> Ah right, it was "copied" from alloc_frozen_pages_nolock_noprof() where it's
> explained more, and AFAICS will be still applicable with sheaves. We should
> add a comment to kmalloc_nolock() referring to the
> alloc_frozen_pages_nolock_noprof() comment...

Right. This looks halfway what I remember. And this was works in atomic
context on RT because of rmqueue_pcplist()/ pcp_spin_trylock() usage.

Sebastian