From: Joel Fernandes <joel@joelfernandes.org>
To: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Josh Triplett <josh@joshtriplett.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
byungchul.park@lge.com, kernel-team@android.com
Subject: Re: [PATCH RFC 1/8] rcu: Add comment documenting how rcu_seq_snap works
Date: Sun, 13 May 2018 22:05:36 -0700 [thread overview]
Message-ID: <20180514050536.GB80415@joelaf.mtv.corp.google.com> (raw)
In-Reply-To: <d13d5fca-d98c-c657-316d-aed10fd3eff0@infradead.org>
On Sun, May 13, 2018 at 08:47:24PM -0700, Randy Dunlap wrote:
> On 05/13/2018 08:15 PM, Joel Fernandes (Google) wrote:
> > rcu_seq_snap may be tricky for someone looking at it for the first time.
> > Lets document how it works with an example to make it easier.
> >
> > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> > ---
> > kernel/rcu/rcu.h | 24 +++++++++++++++++++++++-
> > 1 file changed, 23 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
> > index 003671825d62..fc3170914ac7 100644
> > --- a/kernel/rcu/rcu.h
> > +++ b/kernel/rcu/rcu.h
> > @@ -91,7 +91,29 @@ static inline void rcu_seq_end(unsigned long *sp)
> > WRITE_ONCE(*sp, rcu_seq_endval(sp));
> > }
> >
> > -/* Take a snapshot of the update side's sequence number. */
> > +/*
> > + * Take a snapshot of the update side's sequence number.
> > + *
> > + * This function predicts what the grace period number will be the next
> > + * time an RCU callback will be executed, given the current grace period's
> > + * number. This can be gp+1 if RCU is idle, or gp+2 if a grace period is
> > + * already in progress.
> > + *
> > + * We do this with a single addition and masking.
> > + * For example, if RCU_SEQ_STATE_MASK=1 and the least significant bit (LSB) of
> > + * the seq is used to track if a GP is in progress or not, its sufficient if we
>
> it's
Pardon my english. Fixed, thanks,
- Joel
next prev parent reply other threads:[~2018-05-14 5:05 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-14 3:15 [PATCH RFC 0/8] rcu fixes, clean ups for rcu/dev Joel Fernandes (Google)
2018-05-14 3:15 ` [PATCH RFC 1/8] rcu: Add comment documenting how rcu_seq_snap works Joel Fernandes (Google)
2018-05-14 3:47 ` Randy Dunlap
2018-05-14 5:05 ` Joel Fernandes [this message]
2018-05-14 17:38 ` Paul E. McKenney
2018-05-15 1:51 ` Joel Fernandes
2018-05-15 3:59 ` Paul E. McKenney
2018-05-15 7:02 ` Joel Fernandes
2018-05-15 12:55 ` Paul E. McKenney
2018-05-15 18:41 ` Joel Fernandes
2018-05-15 19:08 ` Paul E. McKenney
2018-05-15 22:55 ` Joel Fernandes
2018-05-16 15:45 ` Paul E. McKenney
2018-05-16 23:21 ` Joel Fernandes
2018-05-14 3:15 ` [PATCH RFC 2/8] rcu: Clarify usage of cond_resched for tasks-RCU Joel Fernandes (Google)
2018-05-14 14:54 ` Steven Rostedt
2018-05-14 17:22 ` Paul E. McKenney
2018-05-15 0:35 ` Joel Fernandes
2018-05-15 3:42 ` Paul E. McKenney
2018-05-14 3:15 ` [PATCH RFC 3/8] rcu: Add back the cpuend tracepoint Joel Fernandes (Google)
2018-05-14 18:12 ` Paul E. McKenney
2018-05-15 0:43 ` Joel Fernandes
2018-05-14 3:15 ` [PATCH RFC 4/8] rcu: Get rid of old c variable from places in tree RCU Joel Fernandes (Google)
2018-05-14 17:57 ` Paul E. McKenney
2018-05-15 0:41 ` Joel Fernandes
2018-05-14 3:15 ` [PATCH RFC 5/8] rcu: Use rcu_node as temporary variable in funnel locking loop Joel Fernandes (Google)
2018-05-14 18:00 ` Paul E. McKenney
2018-05-15 0:43 ` Joel Fernandes
2018-05-14 3:15 ` [PATCH RFC 6/8] rcu: Add back the Startedleaf tracepoint Joel Fernandes (Google)
2018-05-14 18:38 ` Paul E. McKenney
2018-05-15 0:57 ` Joel Fernandes
2018-05-15 3:46 ` Paul E. McKenney
2018-05-15 23:04 ` Joel Fernandes
2018-05-16 15:48 ` Paul E. McKenney
2018-05-16 23:13 ` Joel Fernandes
2018-05-14 3:15 ` [PATCH RFC 7/8] rcu: trace CleanupMore condition only if needed Joel Fernandes (Google)
2018-05-14 19:20 ` Paul E. McKenney
2018-05-15 1:01 ` Joel Fernandes
2018-05-15 3:47 ` Paul E. McKenney
2018-05-14 3:15 ` [PATCH RFC 8/8] rcu: Fix cpustart tracepoint gp_seq number Joel Fernandes (Google)
2018-05-14 20:33 ` Paul E. McKenney
2018-05-15 1:02 ` Joel Fernandes
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=20180514050536.GB80415@joelaf.mtv.corp.google.com \
--to=joel@joelfernandes.org \
--cc=byungchul.park@lge.com \
--cc=jiangshanlai@gmail.com \
--cc=josh@joshtriplett.org \
--cc=kernel-team@android.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=rdunlap@infradead.org \
--cc=rostedt@goodmis.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).