mono/metadata/sgen-os-posix.c

   1 /*
   2  * sgen-os-posix.c: Posix support.
   3  *
   4  * Author:
   5  *      Paolo Molaro (lupus@ximian.com)
   6  *      Mark Probst (mprobst@novell.com)
   7  *      Geoff Norton (gnorton@novell.com)
   8  *
   9  * Copyright 2010 Novell, Inc (http://www.novell.com)
  10  * Copyright (C) 2012 Xamarin Inc
  11  *
  12  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
  13  */
  14
  15 #include "config.h"
  16
  17 #if defined(HAVE_SGEN_GC) && !defined(USE_COOP_GC)
  18 #if !defined(__MACH__) && !MONO_MACH_ARCH_SUPPORTED && defined(HAVE_PTHREAD_KILL)
  19
  20 #include <errno.h>
  21 #include <glib.h>
  22 #include "sgen/sgen-gc.h"
  23 #include "metadata/gc-internals.h"
  24 #include "sgen/sgen-archdep.h"
  25 #include "metadata/object-internals.h"
  26 #include "utils/mono-signal-handler.h"
  27
  28 #if defined(__APPLE__) || defined(__OpenBSD__) || defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
  29 const static int suspend_signal_num = SIGXFSZ;
  30 #else
  31 const static int suspend_signal_num = SIGPWR;
  32 #endif
  33 const static int restart_signal_num = SIGXCPU;
  34
  35 static SgenSemaphore suspend_ack_semaphore;
  36 static SgenSemaphore *suspend_ack_semaphore_ptr;
  37
  38 static sigset_t suspend_signal_mask;
  39 static sigset_t suspend_ack_signal_mask;
  40
  41 static void
  42 suspend_thread (SgenThreadInfo *info, void *context)
  43 {
  44         int stop_count;
  45         MonoContext ctx;
  46         gpointer stack_start;
  47
  48         info->client_info.stopped_domain = mono_domain_get ();
  49         info->client_info.signal = 0;
  50         stop_count = sgen_global_stop_count;
  51         /* duplicate signal */
  52         if (0 && info->client_info.stop_count == stop_count)
  53                 return;
  54
  55         if (context) {
  56                 mono_sigctx_to_monoctx (context, &ctx);
  57                 info->client_info.stopped_ip = MONO_CONTEXT_GET_IP (&ctx);
  58                 stack_start = (((guint8 *) MONO_CONTEXT_GET_SP (&ctx)) - REDZONE_SIZE);
  59         } else {
  60                 info->client_info.stopped_ip = NULL;
  61                 stack_start = NULL;
  62         }
  63
  64         /* If stack_start is not within the limits, then don't set it
  65            in info and we will be restarted. */
  66         if (stack_start >= info->client_info.stack_start_limit && stack_start <= info->client_info.stack_end) {
  67                 info->client_info.stack_start = stack_start;
  68
  69                 if (context) {
  70                         memcpy (&info->client_info.ctx, &ctx, sizeof (MonoContext));
  71                 } else {
  72                         memset (&info->client_info.ctx, 0, sizeof (MonoContext));
  73                 }
  74         } else {
  75                 g_assert (!info->client_info.stack_start);
  76         }
  77
  78         /* Notify the JIT */
  79         if (mono_gc_get_gc_callbacks ()->thread_suspend_func)
  80                 mono_gc_get_gc_callbacks ()->thread_suspend_func (info->client_info.runtime_data, context, NULL);
  81
  82         SGEN_LOG (4, "Posting suspend_ack_semaphore for suspend from %p %p", info, (gpointer) (gsize) mono_native_thread_id_get ());
  83
  84         /*
  85         Block the restart signal.
  86         We need to block the restart signal while posting to the suspend_ack semaphore or we race to sigsuspend,
  87         which might miss the signal and get stuck.
  88         */
  89         pthread_sigmask (SIG_BLOCK, &suspend_ack_signal_mask, NULL);
  90
  91         /* notify the waiting thread */
  92         SGEN_SEMAPHORE_POST (suspend_ack_semaphore_ptr);
  93         info->client_info.stop_count = stop_count;
  94
  95         /* wait until we receive the restart signal */
  96         do {
  97                 info->client_info.signal = 0;
  98                 sigsuspend (&suspend_signal_mask);
  99         } while (info->client_info.signal != restart_signal_num);
 100
 101         /* Unblock the restart signal. */
 102         pthread_sigmask (SIG_UNBLOCK, &suspend_ack_signal_mask, NULL);
 103
 104         SGEN_LOG (4, "Posting suspend_ack_semaphore for resume from %p %p\n", info, (gpointer) (gsize) mono_native_thread_id_get ());
 105         /* notify the waiting thread */
 106         SGEN_SEMAPHORE_POST (suspend_ack_semaphore_ptr);
 107 }
 108
 109 /* LOCKING: assumes the GC lock is held (by the stopping thread) */
 110 MONO_SIG_HANDLER_FUNC (static, suspend_handler)
 111 {
 112         /*
 113          * The suspend signal handler potentially uses syscalls that
 114          * can set errno, and it calls functions that use the hazard
 115          * pointer machinery.  Since we're interrupting other code we
 116          * must restore those to the values they had when we
 117          * interrupted.
 118          */
 119         SgenThreadInfo *info;
 120         int old_errno = errno;
 121         int hp_save_index = mono_hazard_pointer_save_for_signal_handler ();
 122         MONO_SIG_HANDLER_GET_CONTEXT;
 123
 124         info = mono_thread_info_current ();
 125         suspend_thread (info, ctx);
 126
 127         mono_hazard_pointer_restore_for_signal_handler (hp_save_index);
 128         errno = old_errno;
 129 }
 130
 131 MONO_SIG_HANDLER_FUNC (static, restart_handler)
 132 {
 133         SgenThreadInfo *info;
 134         int old_errno = errno;
 135
 136         info = mono_thread_info_current ();
 137         info->client_info.signal = restart_signal_num;
 138         SGEN_LOG (4, "Restart handler in %p %p", info, (gpointer) (gsize) mono_native_thread_id_get ());
 139         errno = old_errno;
 140 }
 141
 142 gboolean
 143 sgen_resume_thread (SgenThreadInfo *info)
 144 {
 145         return mono_threads_pthread_kill (info, restart_signal_num) == 0;
 146 }
 147
 148 gboolean
 149 sgen_suspend_thread (SgenThreadInfo *info)
 150 {
 151         return mono_threads_pthread_kill (info, suspend_signal_num) == 0;
 152 }
 153
 154 void
 155 sgen_wait_for_suspend_ack (int count)
 156 {
 157         int i, result;
 158
 159         for (i = 0; i < count; ++i) {
 160                 while ((result = SGEN_SEMAPHORE_WAIT (suspend_ack_semaphore_ptr)) != 0) {
 161                         if (errno != EINTR) {
 162                                 g_error ("SGEN_SEMAPHORE_WAIT FAILED with %d errno %d (%s)", result, errno, strerror (errno));
 163                         }
 164                 }
 165         }
 166 }
 167
 168 int
 169 sgen_thread_handshake (BOOL suspend)
 170 {
 171         int count, result;
 172         int signum = suspend ? suspend_signal_num : restart_signal_num;
 173
 174         MonoNativeThreadId me = mono_native_thread_id_get ();
 175
 176         count = 0;
 177         mono_thread_info_current ()->client_info.suspend_done = TRUE;
 178         FOREACH_THREAD (info) {
 179                 if (mono_native_thread_id_equals (mono_thread_info_get_tid (info), me)) {
 180                         continue;
 181                 }
 182                 info->client_info.suspend_done = FALSE;
 183                 if (info->client_info.gc_disabled)
 184                         continue;
 185                 /*if (signum == suspend_signal_num && info->stop_count == global_stop_count)
 186                         continue;*/
 187                 result = mono_threads_pthread_kill (info, signum);
 188                 if (result == 0) {
 189                         count++;
 190                 } else {
 191                         info->client_info.skip = 1;
 192                 }
 193         } FOREACH_THREAD_END
 194
 195         sgen_wait_for_suspend_ack (count);
 196
 197         SGEN_LOG (4, "%s handshake for %d threads\n", suspend ? "suspend" : "resume", count);
 198
 199         return count;
 200 }
 201
 202 void
 203 sgen_os_init (void)
 204 {
 205         struct sigaction sinfo;
 206
 207         if (mono_thread_info_unified_management_enabled ())
 208                 return;
 209
 210         suspend_ack_semaphore_ptr = &suspend_ack_semaphore;
 211         SGEN_SEMAPHORE_INIT (&suspend_ack_semaphore, 0);
 212
 213         sigfillset (&sinfo.sa_mask);
 214         sinfo.sa_flags = SA_RESTART | SA_SIGINFO;
 215         sinfo.sa_sigaction = suspend_handler;
 216         if (sigaction (suspend_signal_num, &sinfo, NULL) != 0) {
 217                 g_error ("failed sigaction");
 218         }
 219
 220         sinfo.sa_handler = (void (*)(int))restart_handler;
 221         if (sigaction (restart_signal_num, &sinfo, NULL) != 0) {
 222                 g_error ("failed sigaction");
 223         }
 224
 225         sigfillset (&suspend_signal_mask);
 226         sigdelset (&suspend_signal_mask, restart_signal_num);
 227
 228         sigemptyset (&suspend_ack_signal_mask);
 229         sigaddset (&suspend_ack_signal_mask, restart_signal_num);
 230
 231 }
 232
 233 int
 234 mono_gc_get_suspend_signal (void)
 235 {
 236         return suspend_signal_num;
 237 }
 238
 239 int
 240 mono_gc_get_restart_signal (void)
 241 {
 242         return restart_signal_num;
 243 }
 244 #endif
 245 #endif