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From: Steven Rostedt <rostedt@goodmis.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	Andy Lutomirski <luto@amacapital.net>,
	Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Russell King <linux@arm.linux.org.uk>,
	Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>,
	Ben Maurer <bmaurer@fb.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Joel Fernandes <joelaf@google.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Matthew Wilcox <mawilcox@microsoft.com>
Subject: Re: [RFC PATCH for 4.21 03/16] mm: Replace BUG_ON() by WARN_ON() in vm_unmap_ram()
Date: Thu, 1 Nov 2018 14:46:23 -0400	[thread overview]
Message-ID: <20181101144623.61d43102@gandalf.local.home> (raw)
In-Reply-To: <alpine.DEB.2.21.1811011320160.1642@nanos.tec.linutronix.de>

On Thu, 1 Nov 2018 13:21:12 +0100 (CET)
Thomas Gleixner <tglx@linutronix.de> wrote:

> Mathieu,
> 
> On Thu, 1 Nov 2018, Mathieu Desnoyers wrote:
> 
> > It is encouraged to warn and return rather than use BUG_ON() when
> > the condition can be recovered from in ways that are more graceful than
> > halting the whole system.  
> 
> You're failing to desribe how that graceful recovery works.
> 

I think the graceful recovery is to simply return:

	if (WARN_ON(cond))
		return;

is better than just

	BUG_ON(cond);

As that's what Linus made pretty clear at the Maintainer's Summit.

-- Steve

WARNING: multiple messages have this Message-ID (diff)
From: Steven Rostedt <rostedt@goodmis.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	Andy Lutomirski <luto@amacapital.net>,
	Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Russell King <linux@arm.linux.org.uk>,
	Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>,
	Ben Maurer <bmaurer@fb.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>
Subject: Re: [RFC PATCH for 4.21 03/16] mm: Replace BUG_ON() by WARN_ON() in vm_unmap_ram()
Date: Thu, 1 Nov 2018 14:46:23 -0400	[thread overview]
Message-ID: <20181101144623.61d43102@gandalf.local.home> (raw)
In-Reply-To: <alpine.DEB.2.21.1811011320160.1642@nanos.tec.linutronix.de>

On Thu, 1 Nov 2018 13:21:12 +0100 (CET)
Thomas Gleixner <tglx@linutronix.de> wrote:

> Mathieu,
> 
> On Thu, 1 Nov 2018, Mathieu Desnoyers wrote:
> 
> > It is encouraged to warn and return rather than use BUG_ON() when
> > the condition can be recovered from in ways that are more graceful than
> > halting the whole system.  
> 
> You're failing to desribe how that graceful recovery works.
> 

I think the graceful recovery is to simply return:

	if (WARN_ON(cond))
		return;

is better than just

	BUG_ON(cond);

As that's what Linus made pretty clear at the Maintainer's Summit.

-- Steve

  reply	other threads:[~2018-11-01 18:46 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01  9:58 [RFC PATCH for 4.21 00/16] rseq updates, new cpu_opv system call (v2) Mathieu Desnoyers
2018-11-01  9:58 ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 01/16] rseq/selftests: Expose reference counter to coexist with glibc (v2) Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 02/16] rseq/selftests: Adapt number of threads to the number of detected cpus Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` mathieu.desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 03/16] mm: Replace BUG_ON() by WARN_ON() in vm_unmap_ram() Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01 12:21   ` Thomas Gleixner
2018-11-01 12:21     ` Thomas Gleixner
2018-11-01 18:46     ` Steven Rostedt [this message]
2018-11-01 18:46       ` Steven Rostedt
2018-11-01 19:57       ` Mathieu Desnoyers
2018-11-01 19:57         ` Mathieu Desnoyers
2018-11-01 22:00         ` Linus Torvalds
2018-11-01 22:17           ` Mathieu Desnoyers
2018-11-01 22:17             ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 04/16] mm: Introduce vm_map_user_ram, vm_unmap_user_ram (v2) Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 05/16] mm: Provide is_vma_noncached Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 06/16] cpu_opv: Provide cpu_opv system call (v9) Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 07/16] cpu_opv: limit amount of virtual address space used by cpu_opv Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 08/16] x86: Wire up cpu_opv system call Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 09/16] powerpc: " Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 10/16] arm: " Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 11/16] cpu-opv/selftests: Provide cpu-op library Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` mathieu.desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 12/16] cpu-opv/selftests: Provide basic test Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` mathieu.desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 13/16] cpu-opv/selftests: Provide percpu_op API Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` mathieu.desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 14/16] cpu-opv/selftests: Provide basic percpu ops test Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` mathieu.desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 15/16] cpu-opv/selftests: Provide parametrized tests Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` mathieu.desnoyers
2018-11-01  9:58 ` [RFC PATCH for 4.21 16/16] cpu-opv/selftests: Provide Makefile, scripts, gitignore Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` Mathieu Desnoyers
2018-11-01  9:58   ` mathieu.desnoyers
2018-11-01 15:33 ` [RFC PATCH for 4.21 00/16] rseq updates, new cpu_opv system call (v2) Linus Torvalds

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