From: Peter Zijlstra <peterz@infradead.org>
To: Huacai Chen <chenhc@lemote.com>
Cc: Paul Burton <paul.burton@mips.com>,
Ralf Baechle <ralf@linux-mips.org>,
James Hogan <jhogan@kernel.org>,
Linux MIPS Mailing List <linux-mips@linux-mips.org>,
Fuxin Zhang <zhangfx@lemote.com>,
Zhangjin Wu <wuzhangjin@gmail.com>,
stable <stable@vger.kernel.org>,
Alan Stern <stern@rowland.harvard.edu>,
Andrea Parri <andrea.parri@amarulasolutions.com>,
Will Deacon <will.deacon@arm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Nicholas Piggin <npiggin@gmail.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Akira Yokosawa <akiyks@gmail.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V2] MIPS: implement smp_cond_load_acquire() for Loongson-3
Date: Tue, 10 Jul 2018 12:54:37 +0200 [thread overview]
Message-ID: <20180710105437.GT2512@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180710093637.GF2476@hirez.programming.kicks-ass.net>
On Tue, Jul 10, 2018 at 11:36:37AM +0200, Peter Zijlstra wrote:
> So now explain why the cpu_relax() hack that arm did doesn't work for
> you?
So below is the patch I think you want; if not explain in detail how
this is wrong.
diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index af34afbc32d9..e59773de6528 100644
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -386,7 +386,17 @@ unsigned long get_wchan(struct task_struct *p);
#define KSTK_ESP(tsk) (task_pt_regs(tsk)->regs[29])
#define KSTK_STATUS(tsk) (task_pt_regs(tsk)->cp0_status)
+#ifdef CONFIG_CPU_LOONGSON3
+/*
+ * Loongson-3 has a CPU bug where the store buffer gets starved when stuck in a
+ * read loop. Since spin loops of any kind should have a cpu_relax() in them,
+ * force a store-buffer flush from cpu_relax() such that any pending writes
+ * will become available as expected.
+ */
+#define cpu_relax() smp_mb()
+#else
#define cpu_relax() barrier()
+#endif
/*
* Return_address is a replacement for __builtin_return_address(count)
next prev parent reply other threads:[~2018-07-10 10:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1531103198-16764-1-git-send-email-chenhc@lemote.com>
2018-07-09 16:49 ` [PATCH V2] MIPS: implement smp_cond_load_acquire() for Loongson-3 Paul Burton
2018-07-10 4:26 ` Huacai Chen
2018-07-10 9:36 ` Peter Zijlstra
2018-07-10 10:54 ` Peter Zijlstra [this message]
2018-07-10 11:45 ` 陈华才
2018-07-10 12:17 ` Peter Zijlstra
2018-07-10 16:14 ` Paul E. McKenney
2018-07-10 17:10 ` Paul Burton
2018-07-11 10:04 ` David Laight
2018-07-11 10:55 ` Peter Zijlstra
2018-07-11 10:05 ` Jiaxun Yang
2018-07-11 10:21 ` Will Deacon
2018-07-11 11:09 ` Peter Zijlstra
2018-07-11 11:46 ` David Laight
2018-07-11 9:43 ` Will Deacon
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=20180710105437.GT2512@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=akiyks@gmail.com \
--cc=andrea.parri@amarulasolutions.com \
--cc=boqun.feng@gmail.com \
--cc=chenhc@lemote.com \
--cc=dhowells@redhat.com \
--cc=j.alglave@ucl.ac.uk \
--cc=jhogan@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@linux-mips.org \
--cc=luc.maranget@inria.fr \
--cc=npiggin@gmail.com \
--cc=paul.burton@mips.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=ralf@linux-mips.org \
--cc=stable@vger.kernel.org \
--cc=stern@rowland.harvard.edu \
--cc=will.deacon@arm.com \
--cc=wuzhangjin@gmail.com \
--cc=zhangfx@lemote.com \
/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).