On Mon, 20 Oct 2014 08:00:20 -0400 Prarit Bhargava <prarit@xxxxxxxxxx> wrote: > There have been several times where I have had to rebuild a kernel to > cause a panic when hitting a WARN() in the code in order to get a crash > dump from a system. Sometimes this is easy to do, other times (such as > in the case of a remote admin) it is not trivial to send new images to the > user. > > A much easier method would be a switch to change the WARN() over to a > BUG(). This makes debugging easier in that I can now test the actual > image the WARN() was seen on and I do not have to engage in remote > debugging. > > This patch adds a bug_on_warn kernel parameter, which calls BUG() in the > warn_slowpath_common() path. The function will still print out the > location of the warning. > > Successfully tested by me. Looks nice and simple and useful. However I suspect you're exclusively focussed on "I want a crash dump" and things haven't been fully thought through. - Do you have any example WARN->BUG console output at hand? I'd like to check for missing or duplicated info. - Did you consider permitting this to be tweaked at runtime via /proc? Sometimes we get pesky WARNs at boot time and having runtime alteration would permit the user to prevent those from tripping a BUG. - Also, perhaps bug_on_warn should be single-shot: clear itself after it has triggered one BUG. Because once the kernel has gone WARN->BUG, it's probably messed up and is likely to trigger more WARNs. Also, the kernel might generate many WARNs for the same issue. > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -553,6 +553,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > bttv.pll= See Documentation/video4linux/bttv/Insmod-options > bttv.tuner= > > + bug_on_warn BUG() instead of WARN() There's no mention here that this feature is mainly aimed at generating a crash dump. How do we tell the people who aren't reading this email thread (ie: all of humanity except you and me ;)) that this feature even exists? Is there crash dump documentation that we can update? -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
