From: Peter Zijlstra <peterz@infradead.org>
To: Heiko Carstens <hca@linux.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, Sven Schnelle <svens@linux.ibm.com>
Subject: Re: __local_bh_enable_ip() vs lockdep
Date: Fri, 18 Dec 2020 16:45:19 +0100 [thread overview]
Message-ID: <20201218154519.GW3092@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201218153716.GI3021@hirez.programming.kicks-ass.net>
On Fri, Dec 18, 2020 at 04:37:16PM +0100, Peter Zijlstra wrote:
> On Fri, Dec 18, 2020 at 04:33:56PM +0100, Heiko Carstens wrote:
>
> > Peter, will you make proper patch out of this?
>
> Yes, let me go do that now, and stick it in the quilt series before I go
> off and don't think for 2 weeks.
As below, I'll try and push it out to tip/locking/urgent before I really
dissapear.
---
Subject: softirq: Avoid bad tracing / lockdep interaction
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri Dec 18 16:39:14 CET 2020
Similar to commit:
1a63dcd8765b ("softirq: Reorder trace_softirqs_on to prevent lockdep splat")
__local_bh_enable_ip() can also call into tracing with inconsistent
state. Unlike that commit we don't need to bother about the tracepoint
because 'cnt-1' never matches preempt_count() (by construction).
Reported-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Heiko Carstens <hca@linux.ibm.com>
---
kernel/softirq.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -186,7 +186,7 @@ void __local_bh_enable_ip(unsigned long
* Keep preemption disabled until we are done with
* softirq processing:
*/
- preempt_count_sub(cnt - 1);
+ __preempt_count_sub(cnt - 1);
if (unlikely(!in_interrupt() && local_softirq_pending())) {
/*
next prev parent reply other threads:[~2020-12-18 15:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-15 19:01 __local_bh_enable_ip() vs lockdep Heiko Carstens
2020-12-15 19:47 ` Steven Rostedt
2020-12-16 17:52 ` Peter Zijlstra
2020-12-16 18:35 ` Heiko Carstens
2020-12-18 15:33 ` Heiko Carstens
2020-12-18 15:37 ` Peter Zijlstra
2020-12-18 15:45 ` Peter Zijlstra [this message]
2020-12-18 16:02 ` [tip: locking/urgent] softirq: Avoid bad tracing / lockdep interaction tip-bot2 for Peter Zijlstra
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=20201218154519.GW3092@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=hca@linux.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=svens@linux.ibm.com \
--cc=tglx@linutronix.de \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.