On 12/20/2017 01:01 AM, Arnd Bergmann wrote:
On Tue, Dec 19, 2017 at 11:38 PM, Vineet Gupta
<Vineet.Gupta1@xxxxxxxxxxxx> wrote:
On 12/19/2017 12:13 PM, Arnd Bergmann wrote:
I suppose BUG() implies "dead end" like semantics - which ARC was lacking
before ?
Correct. Using __builtin_trap() here avoids the 'control reaches end of
non-void
function' warnings, but then makes us run into the stack size problem that
I work around with the barrier_before_unreachable().
It would be good if you could give this a quick test to see if you get
sensible
output from the __builtin_trap();
It does, added a BUG() arbit, hits an abort()
...
ISA Extn : atomic ll64 unalign (not used)
: mpy[opt 9] div_rem norm barrel-shift swap minmax swape
BPU : partial match, cache:2048, Predict Table:16384
BUG: failure at ../arch/arc/mm/tlb.c:827/arc_mmu_init()!
Tested-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
I meant whether it prints the right registers and stack trace, but I
assume you tested that and just did not list it above.
Sorry, I didn't realize we are missing the stack trace now which you removed from
the patch - why ? Did u intend to reduce inline generated code for the stack dump
calls - which sounds like a great idea. But it would only work for the synchronous
abort() but not when builtin translates to actual trap inducing instruction.
Hmm, so with the new definition of abort(),
+__weak void abort(void)
+{
+ BUG();
+
+ /* if that doesn't kill us, halt */
+ panic("Oops failed to kill thread");
+}
won't that run into an endless recursion? Or do you then override abort()
for ARC?
Indeed so. I didn't run into this in my testing as my for-curr has an ARC specific
version (predating Sudip's generic version- because of build failures in our
internal regression jobs etc). That version only calls panic.
abort() is only likely to be called due to __builtin_trap() for arches where gcc
doesn't have a target specific defn of it. And thus adding the call from BUG()
will cause the recursion as you found out with Sudip's generic version and thus
needs a fixup.
Thx,
-Vineet
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