From: John David Anglin <dave.anglin@bell.net>
To: linux-parisc <linux-parisc@vger.kernel.org>
Cc: Helge Deller <deller@gmx.de>,
James Bottomley <James.Bottomley@HansenPartnership.com>
Subject: [PATCH] parisc: Use ordered store to release TLB lock
Date: Tue, 21 Jul 2020 07:57:01 -0400 [thread overview]
Message-ID: <81ff8f16-2ff5-195a-b6d5-d7e3c970d097@bell.net> (raw)
The LDCW barriers in the tlb_lock and tlb_unlock0 macros can be removed.
In tlb_lock, the barrier isn't needed because there are no prior accesses to be concerned about.
In tlb_unlock0, we replace the LDCW barrier with an ordered store. This ensures that all prior
accesses are performed before the store is performed.
Signed-off-by: Dave Anglin <dave.anglin@bell.net>
---
diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index 4b484ec7c7da..60b966b29d6c 100644
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -454,7 +454,6 @@
nop
LDREG 0(\ptp),\pte
bb,<,n \pte,_PAGE_PRESENT_BIT,3f
- LDCW 0(\tmp),\tmp1
b \fault
stw \spc,0(\tmp)
99: ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
@@ -464,13 +463,16 @@
3:
.endm
- /* Release pa_tlb_lock lock without reloading lock address. */
+ /* Release pa_tlb_lock lock without reloading lock address.
+ Note that the values in the register spc are limited to
+ NR_SPACE_IDS (262144). Thus, the stw instruction always
+ stores a nonzero value even when register spc is 64 bits.
+ We use an ordered store to ensure all prior accesses are
+ performed prior to releasing the lock. */
.macro tlb_unlock0 spc,tmp,tmp1
#ifdef CONFIG_SMP
98: or,COND(=) %r0,\spc,%r0
- LDCW 0(\tmp),\tmp1
- or,COND(=) %r0,\spc,%r0
- stw \spc,0(\tmp)
+ stw,ma \spc,0(\tmp)
99: ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
#endif
.endm
reply other threads:[~2020-07-21 11:57 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
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=81ff8f16-2ff5-195a-b6d5-d7e3c970d097@bell.net \
--to=dave.anglin@bell.net \
--cc=James.Bottomley@HansenPartnership.com \
--cc=deller@gmx.de \
--cc=linux-parisc@vger.kernel.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).