On Thu, Jul 6, 2017 at 12:19 PM, Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx> wrote: > In commit (51cfbc90a5 "fix: kill unreachable BBs after killing a child") > kill_unreachable_bbs() was called during simplification in order > to avoid creating fake cycles between phis and issuing bogus > "crazy programmer" warnings. > > However, simplification is done via cse.c:clean_up_insns() > which is looping over all BBs while kill_unreachable_bbs() > loops over all BBs *and* can delete some of them which may > corrupt the looping in clean_up_insns(). > > Fix this, by adding a flag to kill_unreachable_bbs(), telling > if it is safe to delete the BBs or if we can just mark them > as unreachable (set bb->ep to NULL and unlink any parent and/or > chilren), in which case the deletion will be done later. > > Note: the reproducer is one with very broken syntax but nothing > seems to forbid the same situation to happen with a valid > program. > > Fixes: 51cfbc90a5e1462fcd624a1598ecd985a508a5d6 > Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx> Thanks for catching it. That is a very serious bug. The release will be on hold until this bug has been fix. It is actually more than one of them. I will send out a separate patch catching this kind of behavior. When the parent is doing the loop on this, the lower level caller remove the list element is very hasty. > -void kill_unreachable_bbs(struct entrypoint *ep) > +void kill_unreachable_bbs(struct entrypoint *ep, int del) > { > struct basic_block *bb; > unsigned long generation = ++bb_generation; > @@ -837,7 +837,8 @@ void kill_unreachable_bbs(struct entrypoint *ep) > /* Mark it as being dead */ > kill_bb(bb); > bb->ep = NULL; > - DELETE_CURRENT_PTR(bb); > + if (del) > + DELETE_CURRENT_PTR(bb); > } END_FOR_EACH_PTR(bb); > PACK_PTR_LIST(&ep->bbs); > Well, it can happen to other ptr list as well. And it did. For this one, I thing it is simpler just move the kill_unreachable_bbs() to the outer stage. Some thing like this, what do you say? It did pass the validation test you send out on this patch. >From c4ef6086b07cdf1d0d1790a274ba056910b00b44 Mon Sep 17 00:00:00 2001 From: Christopher Li <sparse@xxxxxxxxxxx> Date: Thu, 6 Jul 2017 16:25:38 -0700 Subject: [PATCH 1/2] move kill_unreachable_bbs to outer cse stage --- cse.c | 3 +++ linearize.c | 3 --- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/cse.c b/cse.c index 0d3815c..af9863f 100644 --- a/cse.c +++ b/cse.c @@ -387,6 +387,9 @@ repeat: } } + if (repeat_phase & REPEAT_CFG_CLEANUP) + kill_unreachable_bbs(ep); + if (repeat_phase & REPEAT_SYMBOL_CLEANUP) simplify_memops(ep); diff --git a/linearize.c b/linearize.c index 7313e72..a367207 100644 --- a/linearize.c +++ b/linearize.c @@ -671,9 +671,6 @@ void insert_branch(struct basic_block *bb, struct instruction *jmp, struct basic remove_parent(child, bb); } END_FOR_EACH_PTR(child); PACK_PTR_LIST(&bb->children); - - if (repeat_phase & REPEAT_CFG_CLEANUP) - kill_unreachable_bbs(bb->ep); } -- 2.9.4 -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html