[uclibc-ng-devel] Unwinding info for cancellable syscalls

Max Filippov jcmvbkbc at gmail.com
Mon Sep 14 04:02:56 CEST 2015


Hello,

I've noticed that several NPTL tst-cancelx* tests fail on ARM, because functions
invoking cancellable syscalls are compiled without -fasynchronous-unwind-tables
making it impossible for the libgcc DWARF unwinder to unwind stack past the
syscall and call the cleanup routine. They work on x86_64, because x86_64 gcc
has -fasynchronous-unwind-tables enabled by default, and on xtensa because it
uses custom unwinding code. I haven't checked, but AFAIU it should fail on other
architectures that use DWARF unwinder. Can anybody confirm that?

I guess that at least all functions that invoke cancellable syscalls
need to be built
with -fasynchronous-unwind-tables in their CFLAGS. I've tried that
with couple of
functions and it fixes corresponding tests. And that's what glibc does in
nptl/Makefile. Does that sound right for uClibc?

-- 
Thanks.
-- Max


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