On Thu, 19 Sep 2013, Chen,Gang( e??a??) wrote:

> PleaseA searchA BUG_ON()A inA kernelA wideA sourceA code,A weA canA knowA whether
> itA isA commonlyA usedA orA not.
> 
> PleaseA searchA BUGA inA arch/A sub-system,A weA canA knowA whichA architectures
> customizeA BUG/BUG_ON.
> 
> AfterA doA theA 2A things,A InA myA opinion,A weA canA treatA BUG/BUG_ON()A isA common
> implementation,A andA mostA ofA architecturesA usesA theA defaultA one.
> 
> PleaseA checkA again,A thanks.
> 

BUG_ON() is used for fatal conditions where continuing could potentially 
be harmful.  Obviously it is commonly used in a kernel.  That doesn't mean 
we BUG_ON() when a string hasn't been defined for a mempolicy mode.  
mpol_to_str() is not critical.

It is not a fatal condition, and nothing you say is going to convince 
anybody on this thread that it's a fatal condition.

> >A That'sA absolutelyA insane.A A IfA codeA isA notA allocatingA enoughA memoryA forA theA 
> >A maximumA possibleA lengthA ofA aA stringA toA beA storedA byA mpol_to_str(),A it'sA aA 
> >A bugA inA theA code.A A WeA doA notA panicA andA rebootA theA user'sA machineA forA suchA aA 
> >A bug.A A Instead,A weA breakA theA buildA andA requireA theA brokenA codeA toA beA fixed.
> >A 
> 
> PleaseA sayA inA polite.
> 

You want a polite response when you're insisting that we declare absolute 
failure, BUG_ON(), stop, and reboot the kernel because a mempolicy mode 
isn't defined as a string in mpol_to_str()?  That sounds like an impolite 
response to the user, so see my politeness to you as coming from the users 
of the systems you just crashed.

This is a compile-time problem, not run-time.

> CanA youA beA sure,A theA "maxlenA ==A 50"A inA "fs/proc/task_mmu()",A mustA beA aA bug??
> 

I asked you to figure out the longest string possible to be stored by 
mpol_to_str().  There's nothing mysterious about that function.  It's 
deterministic.  If you really can't figure out the value this should be, 
then you shouldn't be touching mpol_to_str().