nix-super/boehmgc-coroutine-sp-fallback.diff
Robert Hensing 57409244ec boehmgc: Crude support for coroutines
Fixes the problem where a stack pointer outside the original
thread causes the collector to crash.

It could be made more accurate by recording the stack pointer
every time we switch to a coroutine. We can use this information
to update our own coroutine stacks like normal data. When the
stack pointer is on a thread, we can add a field to GC_thread
"fallback_sp" to be used when the thread sp is outside the original
thread range.
2021-06-24 18:17:03 +02:00

44 lines
1.9 KiB
Diff

diff --git a/pthread_stop_world.c b/pthread_stop_world.c
index 1cee6a0b..8977b0dd 100644
--- a/pthread_stop_world.c
+++ b/pthread_stop_world.c
@@ -674,6 +674,8 @@ GC_INNER void GC_push_all_stacks(void)
struct GC_traced_stack_sect_s *traced_stack_sect;
pthread_t self = pthread_self();
word total_size = 0;
+ size_t stack_limit;
+ pthread_attr_t pattr;
if (!EXPECT(GC_thr_initialized, TRUE))
GC_thr_init();
@@ -723,6 +725,30 @@ GC_INNER void GC_push_all_stacks(void)
hi = p->altstack + p->altstack_size;
/* FIXME: Need to scan the normal stack too, but how ? */
/* FIXME: Assume stack grows down */
+ } else {
+ if (pthread_getattr_np(p->id, &pattr)) {
+ ABORT("GC_push_all_stacks: pthread_getattr_np failed!");
+ }
+ if (pthread_attr_getstacksize(&pattr, &stack_limit)) {
+ ABORT("GC_push_all_stacks: pthread_attr_getstacksize failed!");
+ }
+ // When a thread goes into a coroutine, we lose its original sp until
+ // control flow returns to the thread.
+ // While in the coroutine, the sp points outside the thread stack,
+ // so we can detect this and push the entire thread stack instead,
+ // as an approximation.
+ // We assume that the coroutine has similarly added its entire stack.
+ // This could be made accurate by cooperating with the application
+ // via new functions and/or callbacks.
+ #ifndef STACK_GROWS_UP
+ if (lo >= hi || lo < hi - stack_limit) { // sp outside stack
+ lo = hi - stack_limit;
+ }
+ #else
+ if (lo < hi || lo >= hi + stack_limit) { // sp outside stack
+ lo = hi + stack_limit;
+ }
+ #endif
}
GC_push_all_stack_sections(lo, hi, traced_stack_sect);
# ifdef STACK_GROWS_UP