Use safepoint to deliver SIGINT

* Remove unnecessary sigatomic
* Make flisp calls sigatomic
* Make type inference calls sigatomic
* Refactor interthread communication through signal
* Make sure `sleep` is aborted on `SIGINT` on Linux to deliver the exception faster
* Implement force signal throwing when `SIGINT` arrives too frequently
* Hack to abort io syscall on `SIGINT`

Fix #1468; Fix #2622; Towards #14675

base/inference.jl

@@ -1562,6 +1562,7 @@ function typeinf_loop(frame)
  frame.inworkq || typeinf_frame(frame)
  return
  end
+ ccall(:jl_sigatomic_begin, Void, ())
  try
  in_typeinf_loop = true
  # the core type-inference algorithm
@@ -1608,6 +1609,7 @@ function typeinf_loop(frame)
  println(ex)
  ccall(:jlbacktrace, Void, ())
  end
+ ccall(:jl_sigatomic_end, Void, ())
  nothing
 end
 

src/ast.c

@@ -230,6 +230,7 @@ static jl_ast_context_list_t *jl_ast_ctx_freed = NULL;
 
 static jl_ast_context_t *jl_ast_ctx_enter(void)
 {
+ JL_SIGATOMIC_BEGIN();
  JL_LOCK_NOGC(&flisp_lock);
  jl_ast_context_list_t *node;
  jl_ast_context_t *ctx;
@@ -267,6 +268,7 @@ static jl_ast_context_t *jl_ast_ctx_enter(void)
 
 static void jl_ast_ctx_leave(jl_ast_context_t *ctx)
 {
+ JL_SIGATOMIC_END();
  if (--ctx->ref)
  return;
  JL_LOCK_NOGC(&flisp_lock);
@@ -285,6 +287,8 @@ void jl_init_frontend(void)
  jl_ast_main_ctx.task = jl_current_task;
  jl_ast_context_list_insert(&jl_ast_ctx_using, &jl_ast_main_ctx.list);
  jl_init_ast_ctx(&jl_ast_main_ctx);
+ // To match the one in jl_ast_ctx_leave
+ JL_SIGATOMIC_BEGIN();
  jl_ast_ctx_leave(&jl_ast_main_ctx);
 }
 
@@ -758,6 +762,7 @@ jl_value_t *jl_parse_eval_all(const char *fname, size_t len,
  form = scm_to_julia(fl_ctx, expansion, 0);
  jl_sym_t *head = NULL;
  if (jl_is_expr(form)) head = ((jl_expr_t*)form)->head;
+ JL_SIGATOMIC_END();
  if (head == jl_incomplete_sym)
  jl_errorf("syntax: %s", jl_string_data(jl_exprarg(form,0)));
  else if (head == error_sym)
@@ -766,6 +771,7 @@ jl_value_t *jl_parse_eval_all(const char *fname, size_t len,
  jl_lineno = jl_unbox_long(jl_exprarg(form,0));
  else
  result = jl_toplevel_eval_flex(form, 1);
+ JL_SIGATOMIC_BEGIN();
  ast = cdr_(ast);
  }
  }

src/builtins.c

@@ -194,17 +194,14 @@ JL_CALLABLE(jl_f_throw)
 
 JL_DLLEXPORT void jl_enter_handler(jl_handler_t *eh)
 {
- JL_SIGATOMIC_BEGIN();
+ // Must have no safepoint
  eh->prev = jl_current_task->eh;
  eh->gcstack = jl_pgcstack;
 #ifdef JULIA_ENABLE_THREADING
  eh->gc_state = jl_gc_state();
  eh->locks_len = jl_current_task->locks.len;
 #endif
  jl_current_task->eh = eh;
- // TODO: this should really go after setjmp(). see comment in
- // ctx_switch in task.c.
- JL_SIGATOMIC_END();
 }
 
 JL_DLLEXPORT void jl_pop_handler(int n)

src/debuginfo.cpp

@@ -1674,9 +1674,7 @@ void RTDyldMemoryManagerUnix::registerEHFrames(uint8_t *Addr,
  di->start_ip = start_ip;
  di->end_ip = end_ip;
 
- JL_SIGATOMIC_BEGIN();
  _U_dyn_register(di);
- JL_SIGATOMIC_END();
 }
 
 void RTDyldMemoryManagerUnix::deregisterEHFrames(uint8_t *Addr,

src/init.c

@@ -528,6 +528,11 @@ static void jl_resolve_sysimg_location(JL_IMAGE_SEARCH rel)
  jl_options.load = abspath(jl_options.load);
 }
 
+static void jl_set_io_wait(int v)
+{
+ jl_get_ptls_states()->io_wait = v;
+}
+
 void _julia_init(JL_IMAGE_SEARCH rel)
 {
 #ifdef JULIA_ENABLE_THREADING
@@ -536,6 +541,7 @@ void _julia_init(JL_IMAGE_SEARCH rel)
 #endif
  jl_safepoint_init();
  libsupport_init();
+ ios_set_io_wait_func = jl_set_io_wait;
  jl_io_loop = uv_default_loop(); // this loop will internal events (spawning process etc.),
  // best to call this first, since it also initializes libuv
  restore_signals();

src/jlapi.c

@@ -229,7 +229,7 @@ JL_DLLEXPORT void jl_sigatomic_begin(void)
 
 JL_DLLEXPORT void jl_sigatomic_end(void)
 {
- if (jl_defer_signal == 0)
+ if (jl_get_ptls_states()->defer_signal == 0)
  jl_error("sigatomic_end called in non-sigatomic region");
  JL_SIGATOMIC_END();
 }

src/julia.h

@@ -635,6 +635,7 @@ JL_DLLEXPORT void jl_clear_malloc_data(void);
 // GC write barriers
 JL_DLLEXPORT void jl_gc_queue_root(jl_value_t *root); // root isa jl_value_t*
 
+// Do NOT put a safepoint here
 STATIC_INLINE void jl_gc_wb(void *parent, void *ptr)
 {
  // parent and ptr isa jl_value_t*
@@ -1392,20 +1393,16 @@ JL_DLLEXPORT void jl_yield(void);
 
 // async signal handling ------------------------------------------------------
 
-#include <signal.h>
-
-JL_DLLEXPORT extern volatile sig_atomic_t jl_signal_pending;
-JL_DLLEXPORT extern volatile sig_atomic_t jl_defer_signal;
-
-#define JL_SIGATOMIC_BEGIN() jl_atomic_fetch_add(&jl_defer_signal, 1)
-#define JL_SIGATOMIC_END() \
- do { \
- if (jl_atomic_fetch_add(&jl_defer_signal, -1) == 1 \
- && jl_signal_pending != 0) { \
- jl_signal_pending = 0; \
- jl_sigint_action(); \
+#define JL_SIGATOMIC_BEGIN() do { \
+ jl_get_ptls_states()->defer_signal++; \
+ jl_signal_fence(); \
+ } while (0)
+#define JL_SIGATOMIC_END() do { \
+ jl_signal_fence(); \
+ if (--jl_get_ptls_states()->defer_signal == 0) { \
+ jl_sigint_safepoint(); \
  } \
- } while(0)
+ } while (0)
 
 JL_DLLEXPORT void jl_sigint_action(void);
 JL_DLLEXPORT void jl_install_sigint_handler(void);
@@ -1511,7 +1508,6 @@ STATIC_INLINE void jl_eh_restore_state(jl_handler_t *eh)
 {
  // This function should **NOT** have any safepoint before restoring
  // the GC state at the end.
- JL_SIGATOMIC_BEGIN();
  jl_current_task->eh = eh->prev;
  jl_pgcstack = eh->gcstack;
 #ifdef JULIA_ENABLE_THREADING
@@ -1525,7 +1521,6 @@ STATIC_INLINE void jl_eh_restore_state(jl_handler_t *eh)
  // This should be the last since this can trigger a safepoint
  // that throws a SIGINT.
  jl_gc_state_save_and_set(eh->gc_state);
- JL_SIGATOMIC_END();
 }
 
 JL_DLLEXPORT void jl_enter_handler(jl_handler_t *eh);

src/julia_threads.h

@@ -26,6 +26,7 @@
 #ifndef _OS_WINDOWS_
 # include <pthread.h>
 #endif
+#include <signal.h>
 
 // This includes all the thread local states we care about for a thread.
 #define JL_MAX_BT_SIZE 80000
@@ -43,6 +44,7 @@ typedef struct _jl_tls_states_t {
  volatile int8_t gc_state;
  volatile int8_t in_finalizer;
  int8_t disable_gc;
+ volatile sig_atomic_t defer_signal;
  struct _jl_thread_heap_t *heap;
  struct _jl_module_t *current_module;
  struct _jl_task_t *volatile current_task;
@@ -58,6 +60,12 @@ typedef struct _jl_tls_states_t {
  size_t bt_size;
  // JL_MAX_BT_SIZE + 1 elements long
  uintptr_t *bt_data;
+ // Atomically set by the sender, reset by the handler.
+ volatile sig_atomic_t signal_request;
+ // Allow the sigint to be raised asynchronously
+ // this is limited to the few places we do synchronous IO
+ // we can make this more general (similar to defer_signal) if necessary
+ volatile sig_atomic_t io_wait;
 } jl_tls_states_t;
 
 #ifdef __MIC__
@@ -295,6 +303,12 @@ JL_DLLEXPORT JL_CONST_FUNC jl_tls_states_t *(jl_get_ptls_states)(void);
  jl_signal_fence(); \
  (void)safepoint_load; \
  } while (0)
+#define jl_sigint_safepoint() do { \
+ jl_signal_fence(); \
+ size_t safepoint_load = jl_get_ptls_states()->safepoint[-1]; \
+ jl_signal_fence(); \
+ (void)safepoint_load; \
+ } while (0)
 #ifndef JULIA_ENABLE_THREADING
 extern JL_DLLEXPORT jl_tls_states_t jl_tls_states;
 #define jl_get_ptls_states() (&jl_tls_states)

src/safepoint.c

@@ -14,7 +14,10 @@
 extern "C" {
 #endif
 
-/* static uint32_t jl_signal_pending = 0; */
+// 0: no sigint is pending
+// 1: at least one sigint is pending, only the sigint page is enabled.
+// 2: at least one sigint is pending, both safepoint pages are enabled.
+JL_DLLEXPORT sig_atomic_t jl_signal_pending = 0;
 volatile uint32_t jl_gc_running = 0;
 char *jl_safepoint_pages = NULL;
 // The number of safepoints enabled on the three pages.
@@ -168,9 +171,61 @@ void jl_safepoint_wait_gc(void)
 #endif
 }
 
-void jl_safepoint_enable_sigint(void);
-void jl_safepoint_defer_sigint(void);
-int jl_safepoint_consume_sigint(void);
+void jl_safepoint_enable_sigint(void)
+{
+ jl_mutex_lock_nogc(&safepoint_lock);
+ // Make sure both safepoints are enabled exactly once for SIGINT.
+ switch (jl_signal_pending) {
+ default:
+ assert(0 && "Shouldn't happen.");
+ case 0:
+ // Enable SIGINT page
+ jl_safepoint_enable(0);
+ // fall through
+ case 1:
+ // SIGINT page is enabled, enable GC page
+ jl_safepoint_enable(1);
+ // fall through
+ case 2:
+ jl_signal_pending = 2;
+ }
+ jl_mutex_unlock_nogc(&safepoint_lock);
+}
+
+void jl_safepoint_defer_sigint(void)
+{
+ jl_mutex_lock_nogc(&safepoint_lock);
+ // Make sure the GC safepoint is disabled for SIGINT.
+ if (jl_signal_pending == 2) {
+ jl_safepoint_disable(1);
+ jl_signal_pending = 1;
+ }
+ jl_mutex_unlock_nogc(&safepoint_lock);
+}
+
+int jl_safepoint_consume_sigint(void)
+{
+ int has_signal = 0;
+ jl_mutex_lock_nogc(&safepoint_lock);
+ // Make sure both safepoints are disabled for SIGINT.
+ switch (jl_signal_pending) {
+ default:
+ assert(0 && "Shouldn't happen.");
+ case 2:
+ // Disable gc page
+ jl_safepoint_disable(1);
+ // fall through
+ case 1:
+ // GC page is disabled, disable SIGINT page
+ jl_safepoint_disable(0);
+ has_signal = 1;
+ // fall through
+ case 0:
+ jl_signal_pending = 0;
+ }
+ jl_mutex_unlock_nogc(&safepoint_lock);
+ return has_signal;
+}
 
 #ifdef __cplusplus
 }

src/signal-handling.c

@@ -23,11 +23,35 @@ static const uint64_t GIGA = 1000000000ULL;
 JL_DLLEXPORT void jl_profile_stop_timer(void);
 JL_DLLEXPORT int jl_profile_start_timer(void);
 
-volatile sig_atomic_t jl_signal_pending = 0;
-volatile sig_atomic_t jl_defer_signal = 0;
+static uint64_t jl_last_sigint_trigger = 0;
+static void jl_clear_force_sigint(void)
+{
+ jl_last_sigint_trigger = 0;
+}
 
-int exit_on_sigint = 0;
-JL_DLLEXPORT void jl_exit_on_sigint(int on) {exit_on_sigint = on;}
+static int jl_check_force_sigint(void)
+{
+ static double accum_weight = 0;
+ uint64_t cur_time = uv_hrtime();
+ uint64_t dt = cur_time - jl_last_sigint_trigger;
+ uint64_t last_t = jl_last_sigint_trigger;
+ jl_last_sigint_trigger = cur_time;
+ if (last_t == 0) {
+ accum_weight = 0;
+ return 0;
+ }
+ double new_weight = accum_weight * exp(-(dt / 1e9)) + 0.3;
+ if (!isnormal(new_weight))
+ new_weight = 0;
+ accum_weight = new_weight;
+ return new_weight > 1;
+}
+
+static int exit_on_sigint = 0;
+JL_DLLEXPORT void jl_exit_on_sigint(int on)
+{
+ exit_on_sigint = on;
+}
 
 // what to do on SIGINT
 JL_DLLEXPORT void jl_sigint_action(void)