From af9379c7121d5543722c00bbd1adf7dcaa0b6448 Mon Sep 17 00:00:00 2001 From: David Brownell Date: Tue, 6 Jan 2009 14:41:01 -0800 Subject: [PATCH] documentation: when to BUG(), and when to not BUG() Provide some basic advice about when to use BUG()/BUG_ON(): never, unless there's really no better option. This matches my understanding of the standard policy ... which seems not to be written down so far, outside of LKML messages that I haven't bookmarked. Signed-off-by: David Brownell Cc: Hans Verkuil Cc: Ingo Molnar Cc: Arjan van de Ven Cc: Randy Dunlap Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/bug.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h index 8af276361bf2..37b82cb96c89 100644 --- a/include/asm-generic/bug.h +++ b/include/asm-generic/bug.h @@ -28,6 +28,17 @@ struct bug_entry { #define BUGFLAG_WARNING (1<<0) #endif /* CONFIG_GENERIC_BUG */ +/* + * Don't use BUG() or BUG_ON() unless there's really no way out; one + * example might be detecting data structure corruption in the middle + * of an operation that can't be backed out of. If the (sub)system + * can somehow continue operating, perhaps with reduced functionality, + * it's probably not BUG-worthy. + * + * If you're tempted to BUG(), think again: is completely giving up + * really the *only* solution? There are usually better options, where + * users don't need to reboot ASAP and can mostly shut down cleanly. + */ #ifndef HAVE_ARCH_BUG #define BUG() do { \ printk("BUG: failure at %s:%d/%s()!\n", __FILE__, __LINE__, __func__); \ @@ -39,6 +50,12 @@ struct bug_entry { #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while(0) #endif +/* + * WARN(), WARN_ON(), WARN_ON_ONCE, and so on can be used to report + * significant issues that need prompt attention if they should ever + * appear at runtime. Use the versions with printk format strings + * to provide better diagnostics. + */ #ifndef __WARN #ifndef __ASSEMBLY__ extern void warn_slowpath(const char *file, const int line, -- 2.30.2