From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Mateusz Guzik <mjguzik@gmail.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
bpf@vger.kernel.org, andrii@kernel.org, memxor@gmail.com,
akpm@linux-foundation.org, peterz@infradead.org, vbabka@suse.cz,
rostedt@goodmis.org, houtao1@huawei.com, hannes@cmpxchg.org,
shakeel.butt@linux.dev, mhocko@suse.com, willy@infradead.org,
tglx@linutronix.de, jannh@google.com, tj@kernel.org,
linux-mm@kvack.org, kernel-team@fb.com
Subject: Re: [PATCH bpf-next v9 1/6] locking/local_lock: Introduce localtry_lock_t
Date: Tue, 11 Mar 2025 17:20:59 +0100 [thread overview]
Message-ID: <20250311162059.BunTzxde@linutronix.de> (raw)
In-Reply-To: <oswrb2f2mx36l6f624hqjvx4lkjdi26xwfwux2wi2mlzmdmmf2@dpaodu372ldv>
On 2025-03-11 16:44:30 [+0100], Mateusz Guzik wrote:
> On Fri, Feb 21, 2025 at 06:44:22PM -0800, Alexei Starovoitov wrote:
> > +#define __localtry_lock(lock) \
> > + do { \
> > + localtry_lock_t *lt; \
> > + preempt_disable(); \
> > + lt = this_cpu_ptr(lock); \
> > + local_lock_acquire(<->llock); \
> > + WRITE_ONCE(lt->acquired, 1); \
> > + } while (0)
>
> I think these need compiler barriers.
>
> I checked with gcc docs (https://gcc.gnu.org/onlinedocs/gcc/Volatiles.html)
> and found this as confirmation:
> > Accesses to non-volatile objects are not ordered with respect to volatile accesses.
>
> Unless the Linux kernel is built with some magic to render this moot(?).
You say we need a barrier() after the WRITE_ONCE()? If so, we need it in
the whole file…
Sebastian
next prev parent reply other threads:[~2025-03-11 16:21 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-22 2:44 [PATCH bpf-next v9 0/6] bpf, mm: Introduce try_alloc_pages() Alexei Starovoitov
2025-02-22 2:44 ` [PATCH bpf-next v9 1/6] locking/local_lock: Introduce localtry_lock_t Alexei Starovoitov
2025-03-11 15:44 ` Mateusz Guzik
2025-03-11 16:20 ` Sebastian Andrzej Siewior [this message]
2025-03-11 16:31 ` Mateusz Guzik
2025-03-11 20:21 ` Vlastimil Babka
2025-03-11 22:24 ` Alexei Starovoitov
2025-03-12 8:29 ` Vlastimil Babka
2025-03-14 21:05 ` Alexei Starovoitov
2025-03-14 21:08 ` Vlastimil Babka
2025-03-14 21:18 ` Alexei Starovoitov
2025-02-22 2:44 ` [PATCH bpf-next v9 2/6] mm, bpf: Introduce try_alloc_pages() for opportunistic page allocation Alexei Starovoitov
2025-03-11 2:04 ` Andrew Morton
2025-03-11 13:32 ` Alexei Starovoitov
2025-03-11 18:04 ` Mateusz Guzik
2025-03-12 9:45 ` Steven Rostedt
2025-03-15 0:34 ` Alexei Starovoitov
2025-03-12 10:00 ` Vlastimil Babka
2025-03-12 19:06 ` Shakeel Butt
2025-03-13 8:44 ` Michal Hocko
2025-03-13 14:21 ` Vlastimil Babka
2025-03-13 16:02 ` Shakeel Butt
2025-03-14 10:16 ` Michal Hocko
2025-03-15 0:51 ` Alexei Starovoitov
2025-02-22 2:44 ` [PATCH bpf-next v9 3/6] mm, bpf: Introduce free_pages_nolock() Alexei Starovoitov
2025-02-22 2:44 ` [PATCH bpf-next v9 4/6] memcg: Use trylock to access memcg stock_lock Alexei Starovoitov
2025-02-22 2:44 ` [PATCH bpf-next v9 5/6] mm, bpf: Use memcg in try_alloc_pages() Alexei Starovoitov
2025-02-22 2:44 ` [PATCH bpf-next v9 6/6] bpf: Use try_alloc_pages() to allocate pages for bpf needs Alexei Starovoitov
2025-02-26 3:19 ` [PATCH bpf-next v9 0/6] bpf, mm: Introduce try_alloc_pages() Alexei Starovoitov
2025-02-27 17:50 ` patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20250311162059.BunTzxde@linutronix.de \
--to=bigeasy@linutronix.de \
--cc=akpm@linux-foundation.org \
--cc=alexei.starovoitov@gmail.com \
--cc=andrii@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=hannes@cmpxchg.org \
--cc=houtao1@huawei.com \
--cc=jannh@google.com \
--cc=kernel-team@fb.com \
--cc=linux-mm@kvack.org \
--cc=memxor@gmail.com \
--cc=mhocko@suse.com \
--cc=mjguzik@gmail.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=shakeel.butt@linux.dev \
--cc=tglx@linutronix.de \
--cc=tj@kernel.org \
--cc=vbabka@suse.cz \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).