signal: bugfix: sharing of alt stack.

The alternative stack is shared by SIGSEGV and SIGBUS.
Therefore, we cannot tear it down when disabling either
signal; the other may be using it.

* signal.c (stack_refcount): New static variable.
(setup_alt_stack, teardown_alt_stack): Functions removed.
(addref_alt_stack, release_alt_stack): New functions to manage
stack with reference counting.
(set_sig_handler): Rearrange the code to only call addref_alt_stack
when transitioning from no-handler to handler for SIGSEGV and
SIGBUS and to only call release_alt_stack when transitioning
from handler to no-handler for these signals.

0 files changed, 0 insertions, 0 deletions