From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1BDA442C0B for ; Thu, 27 Mar 2025 09:05:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743066318; cv=none; b=oCG4nuoYA57VoQo6BTKrD49KV1MlXjA4dA1QAVoce5sncCM2t/KPrOENBD0mODgeg48QpSbnBWxEILqxD5x6Ge1Nc5qDNi5JOZ5KCRP/ba5fS48rGdN36aFXoU++Hq1q/F/DqU4Z31xRDlbwvsTR1LzgF5/dBNHJFBy9xk8qQ1Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743066318; c=relaxed/simple; bh=RkMbqzjbc432nRH2DHf5PBzhWmoY1DhhHxnl/jiSVgw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RUu6E/13XN6g4nYSCJ3njTxHPI28V5cc6wwDRUyfL1hti6nqNE9aKaVFN6+hgGQTW2EAimlqpo8c/qqUMxlXkzEP6QuElmNjypXh7sky5l73bNFzdwGfG8IwkdCfWmWE7IhZSe98FN+hcg1ANeJKT/VZm+G7Ux95DV9ZCtZ4Ki4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=boJFyhyP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="boJFyhyP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B65AC4CEDD; Thu, 27 Mar 2025 09:05:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743066317; bh=RkMbqzjbc432nRH2DHf5PBzhWmoY1DhhHxnl/jiSVgw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=boJFyhyPBr5Y99lj3ccmHPJ+vhwoKRsSFNJTgWYKHhDP8yXJUU6Aenqp0/DVPvkW0 r7k7YOgRspj+stm3IsRaoIhd5pRfk/539z2zdWvphbIFJ6UGjpNk6t2uNC4RBxy/mf APlCDBC3DLemN9b/QbXg272MCXoa4c6OASAFyEt92sbb98MQfIbC/I1sdaUPZsbTHo s/CYPV/+XqHNZxWgoTPCQQutwBn/9j2zUmM5iJdk5Y+b6XvpdbKCHhBN/oV6yQZVxP EOVD8TeAa+JtNiqHYsKh3dE6ilIky/cRuPXVMin8oSxJm1V51P3dU7mB6uPP1R0VGG TnXNCHpT+9xAQ== Date: Thu, 27 Mar 2025 10:05:14 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [PATCH 5/5] bugs/core: Do not print CPU and PID values in__warn() output Message-ID: References: <20250326084751.2260634-1-mingo@kernel.org> <20250326084751.2260634-6-mingo@kernel.org> <20250326085248.GA25239@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250326085248.GA25239@noisy.programming.kicks-ass.net> * Peter Zijlstra wrote: > On Wed, Mar 26, 2025 at 09:47:50AM +0100, Ingo Molnar wrote: > > For most warnings it's repeated anyway a few lines later, as > > part of the register dump: > > > > WARNING: CPU: 0 PID: 0 at kernel/sched/core.c:8511 sched_init+0x20/0x410 > > ^^^^^^^^^^^^^ > > Modules linked in: > > CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.14.0-01616-g94d7af2844aa #4 PREEMPT(undef) > > ^^^^^^^^^^^^^^^^^^ > > > > In fact the later dump is richer, as it includes the 'comm' line as well. > > > > As a side effect, this makes some space for the 'file' field to be augmented > > with extra information (the condition string in particular). > > > > Signed-off-by: Ingo Molnar > > --- > > kernel/panic.c | 7 ++----- > > 1 file changed, 2 insertions(+), 5 deletions(-) > > > > diff --git a/kernel/panic.c b/kernel/panic.c > > index d8635d5cecb2..3101c21ca39f 100644 > > --- a/kernel/panic.c > > +++ b/kernel/panic.c > > @@ -725,12 +725,9 @@ void __warn(const char *file, int line, void *caller, unsigned taint, > > disable_trace_on_warning(); > > > > if (file) > > - pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n", > > - raw_smp_processor_id(), current->pid, file, line, > > - caller); > > + pr_warn("WARNING: %s:%d at %pS\n", file, line, caller); > > else > > - pr_warn("WARNING: CPU: %d PID: %d at %pS\n", > > - raw_smp_processor_id(), current->pid, caller); > > + pr_warn("WARNING: at %pS\n", caller); > > Over the years I've had concurrent WARNs interleaved on the console. > This duplicate information would allow untangling some of that. Fair enough. With patch #1 below: - Reintroduced CPU and PID - Added a '->comm[]' to the warning line: in practice it's often more valuable than a PID... - Re-ordered the fields of information by value: higher value to lower value. Here's an overview of the output variants (-v3 is the latestest): -vanilla: WARNING: CPU: 0 PID: 0 at kernel/sched/core.c:8511 sched_init+0x20/0x410 -v1: WARNING: CPU: 0 PID: 0 at [ptr == 0 && 1] kernel/sched/core.c:8511 sched_init+0x20/0x410 -v2: WARNING: [ptr == 0 && 1] kernel/sched/core.c:8511 at sched_init+0x20/0x410 -v3: WARNING: [ptr == 0 && 1] kernel/sched/core.c:8511 at sched_init+0x20/0x410 CPU#0: swapper/0 I think I like -v3: a poor guy's single line trace entry in essence. I suppose we'll have some worst-case situations with really complex conditions bloating the output when they trigger, but a quick git grep suggests that most WARN_ON_ONCE() instances are sane, in kernel/ at least. Side note, found some WARN_ON_ONCE() weirdnesses: kernel/sched/syscalls.c: WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0); kernel/sched/syscalls.c: WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0); kernel/sched/syscalls.c: WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0); I don't think WARN_ON()s with complex side effects are considered kernel META these days, right? The pattern in patch #2 below is longer, but less surprising, IMHO. Thanks, Ingo --- kernel/panic.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/kernel/panic.c b/kernel/panic.c index 01746e89a7a1..6478dd70ec6d 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -724,10 +724,15 @@ void __warn(const char *file, int line, void *caller, unsigned taint, disable_trace_on_warning(); - if (file) - pr_warn("WARNING: %s:%d at %pS\n", file, line, caller); - else - pr_warn("WARNING: at %pS\n", caller); + if (file) { + pr_warn("WARNING: %s:%d at %pS CPU#%d: %s/%d\n", + file, line, caller, + raw_smp_processor_id(), current->comm, current->pid); + } else { + pr_warn("WARNING: at %pS CPU#%d: %s/%d\n", + caller, + raw_smp_processor_id(), current->comm, current->pid); + } #pragma GCC diagnostic push #ifndef __clang__ kernel/sched/syscalls.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c index c326de1344fb..1a91231d3ad8 100644 --- a/kernel/sched/syscalls.c +++ b/kernel/sched/syscalls.c @@ -846,7 +846,10 @@ int sched_setscheduler_nocheck(struct task_struct *p, int policy, void sched_set_fifo(struct task_struct *p) { struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 }; - WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0); + int err; + + err = sched_setscheduler_nocheck(p, SCHED_FIFO, &sp); + WARN_ON_ONCE(err); } EXPORT_SYMBOL_GPL(sched_set_fifo);