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fiber: fix crash on GC after forking

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Remove the remainder of ROOT_FIBER_CONTEXT use and unnecessary
differences between the root and non-root fiber.  This makes
it easier to follow new root fiber at fork time.

Multiple sources of truth often leads to bugs, as in this case.
We can determinte root fiber by checking a fiber against the root_fiber
of its owner thread.  The new `fiber_is_root_p' function
supports that.

Now, we can care only about free-ing/recycling/munmap-ing stacks
as appropriate.

[Bug #15050]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64706 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
normal 2018-09-12 20:49:24 +00:00
parent d40694de72
commit 12409ad28c
2 changed files with 28 additions and 24 deletions
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29
cont.c
View file

@ -77,8 +77,7 @@ static long pagesize;
enum context_type {
CONTINUATION_CONTEXT = 0,
FIBER_CONTEXT = 1,
ROOT_FIBER_CONTEXT = 2
FIBER_CONTEXT = 1
};
struct cont_saved_vm_stack {
@ -360,6 +359,12 @@ cont_mark(void *ptr)
RUBY_MARK_LEAVE("cont");
}
static int
fiber_is_root_p(const rb_fiber_t *fib)
{
return fib == fib->cont.saved_ec.thread_ptr->root_fiber;
}
static void
cont_free(void *ptr)
{
@ -378,24 +383,17 @@ cont_free(void *ptr)
/* fiber */
const rb_fiber_t *fib = (rb_fiber_t*)cont;
#ifdef _WIN32
if (cont->type != ROOT_FIBER_CONTEXT) {
if (!fiber_is_root_p(fib)) {
/* don't delete root fiber handle */
if (fib->fib_handle) {
DeleteFiber(fib->fib_handle);
}
}
#else /* not WIN32 */
/* fib->ss_sp == NULL is possible for root fiber */
if (fib->ss_sp != NULL) {
if (cont->type == ROOT_FIBER_CONTEXT) {
rb_bug("Illegal root fiber parameter");
}
munmap((void*)fib->ss_sp, fib->ss_size);
}
else {
/* It may reached here when finalize */
/* TODO examine whether it is a bug */
/* rb_bug("cont_free: release self"); */
}
#endif
}
#else /* not FIBER_USE_NATIVE */
@ -1526,7 +1524,7 @@ root_fiber_alloc(rb_thread_t *th)
rb_fiber_t *fib = th->ec->fiber_ptr;
VM_ASSERT(DATA_PTR(fibval) == NULL);
VM_ASSERT(fib->cont.type == ROOT_FIBER_CONTEXT);
VM_ASSERT(fib->cont.type == FIBER_CONTEXT);
VM_ASSERT(fib->status == FIBER_RESUMED);
th->root_fiber = fib;
@ -1555,7 +1553,7 @@ rb_threadptr_root_fiber_setup(rb_thread_t *th)
{
rb_fiber_t *fib = ruby_mimmalloc(sizeof(rb_fiber_t));
MEMZERO(fib, rb_fiber_t, 1);
fib->cont.type = ROOT_FIBER_CONTEXT;
fib->cont.type = FIBER_CONTEXT;
fib->cont.saved_ec.fiber_ptr = fib;
fib->cont.saved_ec.thread_ptr = th;
fiber_status_set(fib, FIBER_RESUMED); /* skip CREATED */
@ -1571,7 +1569,7 @@ rb_threadptr_root_fiber_release(rb_thread_t *th)
/* ignore. A root fiber object will free th->ec */
}
else {
VM_ASSERT(th->ec->fiber_ptr->cont.type == ROOT_FIBER_CONTEXT);
VM_ASSERT(th->ec->fiber_ptr->cont.type == FIBER_CONTEXT);
VM_ASSERT(th->ec->fiber_ptr->cont.self == 0);
fiber_free(th->ec->fiber_ptr);
@ -1818,7 +1816,7 @@ rb_fiber_resume(VALUE fibval, int argc, const VALUE *argv)
{
rb_fiber_t *fib = fiber_ptr(fibval);
if (fib->prev != 0 || fib->cont.type == ROOT_FIBER_CONTEXT) {
if (fib->prev != 0 || fiber_is_root_p(fib)) {
rb_raise(rb_eFiberError, "double resume");
}
if (fib->transferred != 0) {
@ -1997,7 +1995,6 @@ rb_fiber_atfork(rb_thread_t *th)
if (th->root_fiber) {
if (&th->root_fiber->cont.saved_ec != th->ec) {
th->root_fiber = th->ec->fiber_ptr;
th->root_fiber->cont.type = ROOT_FIBER_CONTEXT;
}
th->root_fiber->prev = 0;
}

23
test/ruby/test_fiber.rb
View file

@ -260,18 +260,25 @@ class TestFiber < Test::Unit::TestCase
end
def test_fork_from_fiber
begin
pid = Process.fork{}
rescue NotImplementedError
return
else
Process.wait(pid)
end
skip 'fork not supported' unless Process.respond_to?(:fork)
pid = nil
bug5700 = '[ruby-core:41456]'
assert_nothing_raised(bug5700) do
Fiber.new do
pid = fork do
Fiber.new {}.transfer
xpid = nil
Fiber.new {
xpid = fork do
# enough to trigger GC on old root fiber
10000.times do
Fiber.new {}.transfer
Fiber.new { Fiber.yield }
end
exit!(0)
end
}.transfer
_, status = Process.waitpid2(xpid)
exit!(status.success?)
end
end.resume
end