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Allow multiple simultaneous interrupts cleanly for #1262

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Instead of setting a flag, each interrupt increments an atomic
counter. When the interrupt is finally handled, either by scheduling
code to run on the event loop or executing some out of band code, the
user must now decrement the interrupt counter with
janet_interpreter_interrupt_handled. While this counter is non-zero, the
event loop will not enter the interpreter. This changes the API a bit but
makes it possible and easy to handle signals without race conditions
or scheduler hacks, as the runtime can ensure that high priority code is
run before re-entering possibly blocking interpreter code again.

Also included is a new function janet_schedule_soon, which prepends to
the task queue instead of appending, allowing interrupt handler to skip
ahead of all other scheduled fibers.

Lastly, also update meson default options to include the
interpreter_interrupt code and raise a runtime error if os/sigaction
is used with interpreter interrupt but that build option is not enabled.
This commit is contained in:
Calvin Rose
2023-08-23 20:14:38 -05:00
parent 21eab7e9cc
commit ffd79c6097
7 changed files with 117 additions and 80 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
src/core/os.c
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@@ -809,6 +809,7 @@ static void close_handle(JanetHandle handle) {
#ifndef JANET_WINDOWS
static void janet_signal_callback(JanetEVGenericMessage msg) {
int sig = msg.tag;
if (msg.argi) janet_interpreter_interrupt_handled(NULL);
Janet handlerv = janet_table_get(&janet_vm.signal_handlers, janet_wrap_integer(sig));
if (!janet_checktype(handlerv, JANET_FUNCTION)) {
/* Let another thread/process try to handle this */
@@ -825,11 +826,8 @@ static void janet_signal_callback(JanetEVGenericMessage msg) {
}
JanetFunction *handler = janet_unwrap_function(handlerv);
JanetFiber *fiber = janet_fiber(handler, 64, 0, NULL);
janet_schedule(fiber, janet_wrap_nil());
if (msg.argi) {
janet_vm.auto_suspend = 0; /* Undo interrupt if it wasn't needed. */
janet_ev_dec_refcount();
}
janet_schedule_soon(fiber, janet_wrap_nil(), JANET_SIGNAL_OK);
janet_ev_dec_refcount();
}
static void janet_signal_trampoline_no_interrupt(int sig) {
@@ -838,6 +836,7 @@ static void janet_signal_trampoline_no_interrupt(int sig) {
memset(&msg, 0, sizeof(msg));
msg.tag = sig;
janet_ev_post_event(&janet_vm, janet_signal_callback, msg);
janet_ev_inc_refcount();
}
static void janet_signal_trampoline(int sig) {
@@ -846,9 +845,9 @@ static void janet_signal_trampoline(int sig) {
memset(&msg, 0, sizeof(msg));
msg.tag = sig;
msg.argi = 1;
janet_interpreter_interrupt(NULL);
janet_ev_post_event(&janet_vm, janet_signal_callback, msg);
janet_ev_inc_refcount();
janet_interpreter_interrupt(NULL);
}
#endif
@@ -881,7 +880,11 @@ JANET_CORE_FN(os_sigaction,
sigfillset(&mask);
memset(&action, 0, sizeof(action));
if (can_interrupt) {
#ifdef JANET_NO_INTERPRETER_INTERRUPT
janet_panic("interpreter interrupt not enabled");
#else
action.sa_handler = janet_signal_trampoline;
#endif
} else {
action.sa_handler = janet_signal_trampoline_no_interrupt;
}