linux-kernel - Re: [PATCH v4 08/22] slab: make percpu sheaves compatible with kmalloc_nolock()/kfree

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Message-ID: <CAADnVQKW2Z62+xC5NUsx4ynqbwPh5yn_EJJrQ4kcPab6KWUK-A@mail.gmail.com>
Date: Fri, 23 Jan 2026 10:05:48 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: 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>, 
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Alexei Starovoitov <ast@...nel.org>, linux-mm <linux-mm@...ck.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	"open list:Real-time Linux (PREEMPT_RT):Keyword:PREEMPT_RT" <linux-rt-devel@...ts.linux.dev>, bpf <bpf@...r.kernel.org>, 
	kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [PATCH v4 08/22] slab: make percpu sheaves compatible with kmalloc_nolock()/kfree_nolock()

On Thu, Jan 22, 2026 at 10:53 PM Vlastimil Babka <vbabka@...e.cz> wrote:
>
> Before we enable percpu sheaves for kmalloc caches, we need to make sure
> kmalloc_nolock() and kfree_nolock() will continue working properly and
> not spin when not allowed to.
>
> Percpu sheaves themselves use local_trylock() so they are already
> compatible. We just need to be careful with the barn->lock spin_lock.
> Pass a new allow_spin parameter where necessary to use
> spin_trylock_irqsave().
>
> In kmalloc_nolock_noprof() we can now attempt alloc_from_pcs() safely,
> for now it will always fail until we enable sheaves for kmalloc caches
> next. Similarly in kfree_nolock() we can attempt free_to_pcs().
>
> Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>
> Reviewed-by: Harry Yoo <harry.yoo@...cle.com>
> Reviewed-by: Hao Li <hao.li@...ux.dev>
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

Acked-by: Alexei Starovoitov <ast@...nel.org>