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From: Jakub Kicinski <kuba@kernel.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>,
	linux-mm@kvack.org, Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-kernel@vger.kernel.org,
	Matthew Wilcox <willy@infradead.org>,
	John Garry <john.garry@huawei.com>,
	linux-block@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [RFC v2 PATCH] mm, sl[au]b: Introduce lockless cache
Date: Thu, 23 Sep 2021 06:28:44 -0700	[thread overview]
Message-ID: <20210923062844.148e08fd@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <688e6750-87e9-fb44-ce40-943bad072e48@kernel.dk>

On Wed, 22 Sep 2021 06:58:00 -0600 Jens Axboe wrote:
> > I considered only case 2) when writing code. Well, To support 1),
> > I think there are two ways:
> > 
> >  a) internally call kmem_cache_free when in_interrupt() is true
> >  b) caller must disable interrupt when freeing
> > 
> > I think a) is okay, how do you think?  
> 
> If the API doesn't support freeing from interrupts, then I'd make that
> the rule. Caller should know better if that can happen, and then just
> use kmem_cache_free() if in a problematic context. That avoids polluting
> the fast path with that check. I'd still make it a WARN_ON_ONCE() as
> described and it can get removed later, hopefully.

Shooting from the hip a little but if I'm getting the context right
this is all very similar to the skb cache so lockdep_assert_in_softirq()
may be useful:

/*
 * Acceptable for protecting per-CPU resources accessed from BH.
 * Much like in_softirq() - semantics are ambiguous, use carefully.
 */
#define lockdep_assert_in_softirq()					\
do {									\
	WARN_ON_ONCE(__lockdep_enabled			&&		\
		     (!in_softirq() || in_irq() || in_nmi()));		\
} while (0)

  parent reply	other threads:[~2021-09-23 13:28 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-20 15:48 Hyeonggon Yoo
2021-09-20 22:01 ` Matthew Wilcox
2021-09-21 10:56   ` Hyeonggon Yoo
2021-09-21 15:42   ` Hyeonggon Yoo
2021-09-21 16:17     ` Matthew Wilcox
2021-09-22  8:32       ` Hyeonggon Yoo
2021-09-22  9:11         ` Hyeonggon Yoo
2021-09-21 15:37 ` Jens Axboe
2021-09-22  8:19   ` Hyeonggon Yoo
2021-09-22 12:58     ` Jens Axboe
2021-09-23  3:34       ` Hyeonggon Yoo
2021-09-23 13:28       ` Jakub Kicinski [this message]
2021-09-23  3:55 ` Github link here Hyeonggon Yoo

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