Re: [PATCH 2/7] genalloc: selftest

[Igor Stoppa]

On 26/02/18 21:12, Matthew Wilcox wrote:
[...]

> panic() halts the kernel
> BUG_ON() kills the thread
> WARN_ON() just prints messages
> 
> Now, if we're at boot time and we're still executing code from the init
> thread, killing init is equivalent to halting the kernel.
> 
> The question is, what is appropriate for test modules?  I would say
> WARN_ON is not appropriate because people ignore warnings.  BUG_ON is
> reasonable for development.  panic() is probably not.

Ok, so I can leave WARN_ON() in the libraries, and keep the more
restrictive BUG_ON() for the self test, which is optional for both
genalloc and pmalloc.

> Also, calling BUG_ON while holding a lock is not a good idea; if anything
> needs to acquire that lock to shut down in a reasonable fashion, it's
> going to hang.
> 
> And there's no need to do something like BUG_ON(!foo); foo->wibble = 1;
> Dereferencing a NULL pointer already produces a nice informative splat.
> In general, we assume other parts of the kernel are sane and if they pass
> us a NULL pool, it's no good returning -EINVAL, we may as well just oops
> and let somebody else debug it.

Great, that makes the code even simpler.

--
igor