Make improvements to locking

This change makes pthread_mutex_lock() as fast as _spinlock() by
default. Thread instability issues on NetBSD have been resolved.
Improvements made to gdtoa thread code. Crash reporting will now
synchronize between threads in a slightly better way.

libc/log/backtrace2.c

@@ -103,12 +103,6 @@ static int PrintBacktraceUsingAddr2line(int fd, const struct StackFrame *bp) {
   garbage = weaken(__garbage);
   gi = garbage ? garbage->i : 0;
   for (frame = bp; frame && i < kBacktraceMaxFrames - 1; frame = frame->next) {
-    __mmi_lock();
-    ok = IsValidStackFramePointer(frame);
-    __mmi_unlock();
-    if (!ok) {
-      return -1;
-    }
     addr = frame->addr;
     if (addr == weakaddr("__gc")) {
       do {

libc/log/backtrace3.c

@@ -57,13 +57,6 @@ noinstrument noasan int PrintBacktraceUsingSymbols(int fd,
   garbage = weaken(__garbage);
   gi = garbage ? garbage->i : 0;
   for (i = 0, frame = bp; frame; frame = frame->next) {
-    __mmi_lock();
-    ok = IsValidStackFramePointer(frame);
-    __mmi_unlock();
-    if (!ok) {
-      kprintf("%p corrupt frame pointer\n", frame);
-      break;
-    }
     if (++i == LIMIT) {
       kprintf("<truncated backtrace>\n");
       break;

libc/log/die.c

@@ -16,8 +16,10 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
 #include "libc/dce.h"
-#include "libc/intrin/lockcmpxchg.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/intrin/lockcmpxchgp.h"
 #include "libc/log/backtrace.internal.h"
 #include "libc/log/internal.h"
 #include "libc/log/libfatal.internal.h"
@@ -32,18 +34,30 @@
  */
 relegated wontreturn void __die(void) {
   /* asan runtime depends on this function */
-  int rc;
-  static bool once;
-  if (_lockcmpxchg(&once, false, true)) {
+  int me, owner;
+  static int sync;
+  owner = 0;
+  me = gettid();
+  if (_lockcmpxchgp(&sync, &owner, me)) {
     __restore_tty();
     if (IsDebuggerPresent(false)) {
       DebugBreak();
     }
-    ShowBacktrace(2, NULL);
-    rc = 77;
+    if (weaken(ShowBacktrace)) {
+      weaken(ShowBacktrace)(2, __builtin_frame_address(0));
+    } else if (weaken(PrintBacktraceUsingSymbols) && weaken(GetSymbolTable)) {
+      weaken(PrintBacktraceUsingSymbols)(2, __builtin_frame_address(0),
+                                         weaken(GetSymbolTable)());
+    } else {
+      kprintf("can't backtrace b/c `ShowCrashReports` not linked\n");
+    }
+    __restorewintty();
+    _Exit(77);
+  } else if (owner == me) {
+    kprintf("die failed while dying\n");
+    __restorewintty();
+    _Exit(78);
   } else {
-    rc = 78;
+    _Exit1(79);
   }
-  __restorewintty();
-  _Exit(rc);
 }

libc/log/oncrash.c

@@ -26,6 +26,7 @@
 #include "libc/intrin/asan.internal.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/intrin/lockcmpxchg.h"
+#include "libc/intrin/lockcmpxchgp.h"
 #include "libc/log/backtrace.internal.h"
 #include "libc/log/gdb.h"
 #include "libc/log/internal.h"
@@ -262,15 +263,22 @@ static wontreturn relegated noinstrument void __minicrash(int sig,
  * simply print addresses which may be cross-referenced using objdump.
  *
  * This function never returns, except for traps w/ human supervision.
+ *
+ * @threadsafe
+ * @vforksafe
  */
 relegated void __oncrash(int sig, struct siginfo *si, ucontext_t *ctx) {
   intptr_t rip;
+  int me, owner;
   int gdbpid, err;
-  static bool noreentry, notpossible;
+  static int sync;
+  static bool notpossible;
   STRACE("__oncrash rip %x", ctx->uc_mcontext.rip);
   --__ftrace;
   --__strace;
-  if (_lockcmpxchg(&noreentry, false, true)) {
+  owner = 0;
+  me = gettid();
+  if (_lockcmpxchgp(&sync, &owner, me)) {
     if (!__vforked) {
       rip = ctx ? ctx->uc_mcontext.rip : 0;
       err = errno;
@@ -292,20 +300,30 @@ relegated void __oncrash(int sig, struct siginfo *si, ucontext_t *ctx) {
         __restorewintty();
         _Exit(128 + sig);
       }
+      sync = 0;
     } else {
+      sync = 0;
       __minicrash(sig, si, ctx, "WHILE VFORKED");
     }
   } else if (sig == SIGTRAP) {
-    /* chances are IsDebuggerPresent() confused strace w/ gdb */
+    // chances are IsDebuggerPresent() confused strace w/ gdb
     goto ItsATrap;
-  } else if (_lockcmpxchg(&notpossible, false, true)) {
-    __minicrash(sig, si, ctx, "WHILE CRASHING");
-  } else {
-    for (;;) {
-      asm("ud2");
+  } else if (owner == me) {
+    // we crashed while generating a crash report
+    if (_lockcmpxchg(&notpossible, false, true)) {
+      __minicrash(sig, si, ctx, "WHILE CRASHING");
+    } else {
+      // somehow __minicrash() crashed not possible
+      for (;;) {
+        asm("ud2");
+      }
     }
+  } else {
+    // multiple threads have crashed
+    // kill current thread assuming process dies soon
+    // TODO(jart): It'd be nice to report on all threads.
+    _Exit1(8);
   }
-  noreentry = false;
 ItsATrap:
   ++__strace;
   ++__ftrace;

libc/log/restoretty.c

@@ -1,68 +0,0 @@
-/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
-│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
-╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
-│                                                                              │
-│ Permission to use, copy, modify, and/or distribute this software for         │
-│ any purpose with or without fee is hereby granted, provided that the         │
-│ above copyright notice and this permission notice appear in all copies.      │
-│                                                                              │
-│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
-│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
-│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
-│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
-│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
-│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
-│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
-│ PERFORMANCE OF THIS SOFTWARE.                                                │
-╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/calls/calls.h"
-#include "libc/calls/struct/metatermios.internal.h"
-#include "libc/calls/struct/termios.h"
-#include "libc/calls/syscall-sysv.internal.h"
-#include "libc/calls/termios.h"
-#include "libc/dce.h"
-#include "libc/errno.h"
-#include "libc/log/color.internal.h"
-#include "libc/log/internal.h"
-#include "libc/log/libfatal.internal.h"
-#include "libc/runtime/internal.h"
-#include "libc/sysv/consts/termios.h"
-
-/**
- * @fileoverview Terminal Restoration Helper for System Five.
- *
- * This is used by the crash reporting functions, e.g. __die(), to help
- * ensure the terminal is in an unborked state after a crash happens.
- */
-
-#define RESET_COLOR   "\e[0m"
-#define SHOW_CURSOR   "\e[?25h"
-#define DISABLE_MOUSE "\e[?1000;1002;1015;1006l"
-#define ANSI_RESTORE  RESET_COLOR SHOW_CURSOR DISABLE_MOUSE
-
-static bool __isrestorable;
-static union metatermios __oldtermios;
-
-static textstartup void __oldtermios_init() {
-  int e;
-  e = errno;
-  if (sys_ioctl(0, TCGETS, &__oldtermios) != -1) {
-    __isrestorable = true;
-  }
-  errno = e;
-}
-
-const void *const __oldtermios_ctor[] initarray = {
-    __oldtermios_init,
-};
-
-void __restore_tty(void) {
-  int e;
-  if (__isrestorable && !__isworker && !__nocolor) {
-    e = errno;
-    sys_write(0, ANSI_RESTORE, __strlen(ANSI_RESTORE));
-    sys_ioctl(0, TCSETSF, &__oldtermios);
-    errno = e;
-  }
-}

libc/log/showcrashreports.c

@@ -30,9 +30,12 @@
 #include "libc/sysv/consts/sig.h"
 #include "libc/sysv/consts/ss.h"
 
-STATIC_YOINK("__die");                /* for backtracing */
-STATIC_YOINK("malloc_inspect_all");   /* for asan memory origin */
-STATIC_YOINK("__get_symbol_by_addr"); /* for asan memory origin */
+STATIC_YOINK("__die");                       // for backtracing
+STATIC_YOINK("ShowBacktrace");               // for backtracing
+STATIC_YOINK("GetSymbolTable");              // for backtracing
+STATIC_YOINK("PrintBacktraceUsingSymbols");  // for backtracing
+STATIC_YOINK("malloc_inspect_all");          // for asan memory origin
+STATIC_YOINK("__get_symbol_by_addr");        // for asan memory origin
 
 extern const unsigned char __oncrash_thunks[8][11];
 static struct sigaltstack g_oldsigaltstack;