From: Alan Huang <mmpgouride@gmail.com>
To: paulmck@kernel.org
Cc: perfbook@vger.kernel.org, Alan Huang <mmpgouride@gmail.com>
Subject: [PATCH] CodeSample/count: Update the places where READ_ONCE is used
Date: Tue, 30 May 2023 14:51:27 +0000 [thread overview]
Message-ID: <20230530145127.18738-1-mmpgouride@gmail.com> (raw)
There is no concurrent updates to 'total' by other threads, plain access
is enough. But there might be threads updating 'counter', READ_ONCE is
required.
Signed-off-by: Alan Huang <mmpgouride@gmail.com>
---
CodeSamples/count/count_end_rcu.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/CodeSamples/count/count_end_rcu.c b/CodeSamples/count/count_end_rcu.c
index 8fc70611..71bd5269 100644
--- a/CodeSamples/count/count_end_rcu.c
+++ b/CodeSamples/count/count_end_rcu.c
@@ -48,10 +48,10 @@ unsigned long read_count(void) //\lnlbl{read:b}
rcu_read_lock(); //\lnlbl{read:rrl}
cap = rcu_dereference(countarrayp); //\lnlbl{read:deref}
- sum = READ_ONCE(cap->total); //\lnlbl{read:init}
+ sum = cap->total; //\lnlbl{read:init}
for_each_thread(t) { //\lnlbl{read:add:b}
ctrp = READ_ONCE(cap->counterp[t]);
- if (ctrp != NULL) sum += *ctrp; //\lnlbl{read:add:e}
+ if (ctrp != NULL) sum += READ_ONCE(*ctrp); //\lnlbl{read:add:e}
}
rcu_read_unlock(); //\lnlbl{read:rru}
return sum; //\lnlbl{read:ret}
--
2.34.1
next reply other threads:[~2023-05-30 14:51 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-30 14:51 Alan Huang [this message]
2023-06-02 20:45 ` [PATCH] CodeSample/count: Update the places where READ_ONCE is used Paul E. McKenney
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=20230530145127.18738-1-mmpgouride@gmail.com \
--to=mmpgouride@gmail.com \
--cc=paulmck@kernel.org \
--cc=perfbook@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 read-only IMAP folder(s) and NNTP newsgroup(s).