From 0dec7ddb341b2b7d2643f86dd9e9497b3f5268a7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn-Egil=20Dahlberg?= <egil@erlang.org>
Date: Tue, 21 Mar 2017 10:48:15 +0100
Subject: erts: Don't allocate memory during signal handling

Allocations and message sending are now scheduled by a signal,
via a signal state bitmap, instead of doing it directly in the signal handler.
---
 erts/emulator/sys/common/erl_check_io.c | 14 ++++++++
 erts/emulator/sys/unix/sys.c            | 64 +++++++++++++++++++++++++++++++--
 2 files changed, 76 insertions(+), 2 deletions(-)

(limited to 'erts/emulator/sys')

diff --git a/erts/emulator/sys/common/erl_check_io.c b/erts/emulator/sys/common/erl_check_io.c
index 1ef9fa2a05..00c70268df 100644
--- a/erts/emulator/sys/common/erl_check_io.c
+++ b/erts/emulator/sys/common/erl_check_io.c
@@ -2169,6 +2169,12 @@ ERTS_CIO_EXPORT(erts_check_io)(int do_wait)
 	erts_do_break_handling();
 #endif
 
+#ifdef ERTS_SIGNAL_STATE /* ifndef ERTS_SMP */
+    if (ERTS_SIGNAL_STATE) {
+        erts_handle_signal_state();
+    }
+#endif
+
     /* Figure out timeout value */
     timeout_time = (do_wait
 		    ? erts_check_next_timeout_time(esdp)
@@ -2207,6 +2213,14 @@ ERTS_CIO_EXPORT(erts_check_io)(int do_wait)
 	erts_do_break_handling();
 #endif
 
+
+#ifdef ERTS_SIGNAL_STATE /* ifndef ERTS_SMP */
+    if (ERTS_SIGNAL_STATE) {
+        erts_handle_signal_state();
+    }
+#endif
+
+
     if (poll_ret != 0) {
 	erts_smp_atomic_set_nob(&pollset.in_poll_wait, 0);
 	forget_removed(&pollset);
diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index e836f9bcc8..b48b3f8804 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -139,6 +139,28 @@ volatile int erts_break_requested = 0;
 #define ERTS_SET_BREAK_REQUESTED (erts_break_requested = 1)
 #define ERTS_UNSET_BREAK_REQUESTED (erts_break_requested = 0)
 #endif
+
+#ifndef ERTS_SMP
+static Eterm signalstate_sigterm[] = {
+    am_sigint,   /* 0 */
+    am_sighup,   /* 1 */
+    am_sigquit,  /* 2 */
+    am_sigabrt,  /* 3 */
+    am_sigalrm,  /* 4 */
+    am_sigterm,  /* 5 */
+    am_sigusr1,  /* 6 */
+    am_sigusr2,  /* 7 */
+    am_sigchld,  /* 8 */
+    am_sigstop,  /* 9 */
+    am_sigtstp   /* 10 */
+};
+
+volatile Uint erts_signal_state = 0;
+#define ERTS_SET_SIGNAL_STATE(S) (erts_signal_state |= signum_to_signalstate(S))
+#define ERTS_CLEAR_SIGNAL_STATE (erts_signal_state = 0)
+static ERTS_INLINE Uint signum_to_signalstate(int signum);
+#endif
+
 /* set early so the break handler has access to initial mode */
 static struct termios initial_tty_mode;
 static int replace_intr = 0;
@@ -770,13 +792,34 @@ signum_to_signalterm(int signum)
     }
 }
 
+#ifndef ERTS_SMP
+static ERTS_INLINE Uint
+signum_to_signalstate(int signum)
+{
+    switch (signum) {
+    case SIGINT:  return (1 <<  0);
+    case SIGHUP:  return (1 <<  1);
+    case SIGQUIT: return (1 <<  2);
+    case SIGABRT: return (1 <<  3);
+    case SIGALRM: return (1 <<  4);
+    case SIGTERM: return (1 <<  5);
+    case SIGUSR1: return (1 <<  6);
+    case SIGUSR2: return (1 <<  7);
+    case SIGCHLD: return (1 <<  8);
+    case SIGSTOP: return (1 <<  9);
+    case SIGTSTP: return (1 << 10);
+    default:      return 0;
+    }
+}
+#endif
+
 static RETSIGTYPE generic_signal_handler(int signum)
 {
 #ifdef ERTS_SMP
     smp_sig_notify(signum);
 #else
-    Eterm signal = signum_to_signalterm(signum);
-    signal_notify_requested(signal);
+    ERTS_SET_SIGNAL_STATE(signum);
+    ERTS_CHK_IO_AS_INTR(); /* Make sure we don't sleep in poll */
 #endif
 }
 
@@ -962,6 +1005,23 @@ void erts_do_break_handling(void)
     erts_smp_thr_progress_unblock();
 }
 
+#ifdef ERTS_SIGNAL_STATE
+void erts_handle_signal_state(void) {
+    Uint signal_state = ERTS_SIGNAL_STATE;
+    Uint i = 0;
+
+    ERTS_CLEAR_SIGNAL_STATE;
+
+    while (signal_state) {
+        if (signal_state & 0x1) {
+            signal_notify_requested(signalstate_sigterm[i]);
+        }
+        i++;
+        signal_state = signal_state >> 1;
+    }
+}
+#endif
+
 /* Fills in the systems representation of the jam/beam process identifier.
 ** The Pid is put in STRING representation in the supplied buffer,
 ** no interpretatione of this should be done by the rest of the
-- 
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