libgo/runtime/panic.c

   1 // Copyright 2012 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 #include "runtime.h"
   6 #include "malloc.h"
   7 #include "go-defer.h"
   8 #include "go-panic.h"
   9
  10 // Code related to defer, panic and recover.
  11
  12 uint32 runtime_panicking;
  13 static Lock paniclk;
  14
  15 // Allocate a Defer, usually using per-P pool.
  16 // Each defer must be released with freedefer.
  17 Defer*
  18 runtime_newdefer()
  19 {
  20         Defer *d;
  21         P *p;
  22
  23         d = nil;
  24         p = runtime_m()->p;
  25         d = p->deferpool;
  26         if(d)
  27                 p->deferpool = d->__next;
  28         if(d == nil) {
  29                 // deferpool is empty
  30                 d = runtime_malloc(sizeof(Defer));
  31         }
  32         return d;
  33 }
  34
  35 // Free the given defer.
  36 // The defer cannot be used after this call.
  37 void
  38 runtime_freedefer(Defer *d)
  39 {
  40         P *p;
  41
  42         if(d->__special)
  43                 return;
  44         p = runtime_m()->p;
  45         d->__next = p->deferpool;
  46         p->deferpool = d;
  47         // No need to wipe out pointers in argp/pc/fn/args,
  48         // because we empty the pool before GC.
  49 }
  50
  51 // Run all deferred functions for the current goroutine.
  52 static void
  53 rundefer(void)
  54 {
  55         G *g;
  56         Defer *d;
  57
  58         g = runtime_g();
  59         while((d = g->defer) != nil) {
  60                 void (*pfn)(void*);
  61
  62                 g->defer = d->__next;
  63                 pfn = d->__pfn;
  64                 d->__pfn = nil;
  65                 if (pfn != nil)
  66                         (*pfn)(d->__arg);
  67                 runtime_freedefer(d);
  68         }
  69 }
  70
  71 void
  72 runtime_startpanic(void)
  73 {
  74         M *m;
  75
  76         m = runtime_m();
  77         if(runtime_mheap.cachealloc.size == 0) { // very early
  78                 runtime_printf("runtime: panic before malloc heap initialized\n");
  79                 m->mallocing = 1; // tell rest of panic not to try to malloc
  80         } else if(m->mcache == nil) // can happen if called from signal handler or throw
  81                 m->mcache = runtime_allocmcache();
  82         switch(m->dying) {
  83         case 0:
  84                 m->dying = 1;
  85                 if(runtime_g() != nil)
  86                         runtime_g()->writebuf = nil;
  87                 runtime_xadd(&runtime_panicking, 1);
  88                 runtime_lock(&paniclk);
  89                 if(runtime_debug.schedtrace > 0 || runtime_debug.scheddetail > 0)
  90                         runtime_schedtrace(true);
  91                 runtime_freezetheworld();
  92                 return;
  93         case 1:
  94                 // Something failed while panicing, probably the print of the
  95                 // argument to panic().  Just print a stack trace and exit.
  96                 m->dying = 2;
  97                 runtime_printf("panic during panic\n");
  98                 runtime_dopanic(0);
  99                 runtime_exit(3);
 100         case 2:
 101                 // This is a genuine bug in the runtime, we couldn't even
 102                 // print the stack trace successfully.
 103                 m->dying = 3;
 104                 runtime_printf("stack trace unavailable\n");
 105                 runtime_exit(4);
 106         default:
 107                 // Can't even print!  Just exit.
 108                 runtime_exit(5);
 109         }
 110 }
 111
 112 void
 113 runtime_dopanic(int32 unused __attribute__ ((unused)))
 114 {
 115         G *g;
 116         static bool didothers;
 117         bool crash;
 118         int32 t;
 119
 120         g = runtime_g();
 121         if(g->sig != 0)
 122                 runtime_printf("[signal %x code=%p addr=%p]\n",
 123                                g->sig, (void*)g->sigcode0, (void*)g->sigcode1);
 124
 125         if((t = runtime_gotraceback(&crash)) > 0){
 126                 if(g != runtime_m()->g0) {
 127                         runtime_printf("\n");
 128                         runtime_goroutineheader(g);
 129                         runtime_traceback();
 130                         runtime_printcreatedby(g);
 131                 } else if(t >= 2 || runtime_m()->throwing > 0) {
 132                         runtime_printf("\nruntime stack:\n");
 133                         runtime_traceback();
 134                 }
 135                 if(!didothers) {
 136                         didothers = true;
 137                         runtime_tracebackothers(g);
 138                 }
 139         }
 140         runtime_unlock(&paniclk);
 141         if(runtime_xadd(&runtime_panicking, -1) != 0) {
 142                 // Some other m is panicking too.
 143                 // Let it print what it needs to print.
 144                 // Wait forever without chewing up cpu.
 145                 // It will exit when it's done.
 146                 static Lock deadlock;
 147                 runtime_lock(&deadlock);
 148                 runtime_lock(&deadlock);
 149         }
 150
 151         if(crash)
 152                 runtime_crash();
 153
 154         runtime_exit(2);
 155 }
 156
 157 bool
 158 runtime_canpanic(G *gp)
 159 {
 160         M *m = runtime_m();
 161         byte g;
 162
 163         USED(&g);  // don't use global g, it points to gsignal
 164
 165         // Is it okay for gp to panic instead of crashing the program?
 166         // Yes, as long as it is running Go code, not runtime code,
 167         // and not stuck in a system call.
 168         if(gp == nil || gp != m->curg)
 169                 return false;
 170         if(m->locks-m->softfloat != 0 || m->mallocing != 0 || m->throwing != 0 || m->gcing != 0 || m->dying != 0)
 171                 return false;
 172         if(gp->status != Grunning)
 173                 return false;
 174 #ifdef GOOS_windows
 175         if(m->libcallsp != 0)
 176                 return false;
 177 #endif
 178         return true;
 179 }
 180
 181 void
 182 runtime_throw(const char *s)
 183 {
 184         M *mp;
 185
 186         mp = runtime_m();
 187         if(mp->throwing == 0)
 188                 mp->throwing = 1;
 189         runtime_startpanic();
 190         runtime_printf("fatal error: %s\n", s);
 191         runtime_dopanic(0);
 192         *(int32*)0 = 0; // not reached
 193         runtime_exit(1);        // even more not reached
 194 }
 195
 196 void
 197 runtime_panicstring(const char *s)
 198 {
 199         Eface err;
 200
 201         if(runtime_m()->mallocing) {
 202                 runtime_printf("panic: %s\n", s);
 203                 runtime_throw("panic during malloc");
 204         }
 205         if(runtime_m()->gcing) {
 206                 runtime_printf("panic: %s\n", s);
 207                 runtime_throw("panic during gc");
 208         }
 209         if(runtime_m()->locks) {
 210                 runtime_printf("panic: %s\n", s);
 211                 runtime_throw("panic holding locks");
 212         }
 213         runtime_newErrorCString(s, &err);
 214         runtime_panic(err);
 215 }
 216
 217 void runtime_Goexit (void) __asm__ (GOSYM_PREFIX "runtime.Goexit");
 218
 219 void
 220 runtime_Goexit(void)
 221 {
 222         rundefer();
 223         runtime_goexit();
 224 }
 225
 226 void
 227 runtime_panicdivide(void)
 228 {
 229         runtime_panicstring("integer divide by zero");
 230 }