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.stack_start = NULL;
  50         info->client_info.signal = 0;
  51         stop_count = sgen_global_stop_count;
  52         /* duplicate signal */
  53         if (0 && info->client_info.stop_count == stop_count)
  54                 return;
  55
  56         if (context) {
  57                 mono_sigctx_to_monoctx (context, &ctx);
  58                 info->client_info.stopped_ip = MONO_CONTEXT_GET_IP (&ctx);
  59                 stack_start = (((guint8 *) MONO_CONTEXT_GET_SP (&ctx)) - REDZONE_SIZE);
  60         } else {
  61                 info->client_info.stopped_ip = NULL;
  62                 stack_start = NULL;
  63         }
  64
  65         /* If stack_start is not within the limits, then don't set it
  66            in info and we will be restarted. */
  67         if (stack_start >= info->client_info.stack_start_limit && stack_start <= info->client_info.stack_end) {
  68                 info->client_info.stack_start = stack_start;
  69
  70                 if (context) {
  71                         memcpy (&info->client_info.ctx, &ctx, sizeof (MonoContext));
  72                 } else {
  73                         memset (&info->client_info.ctx, 0, sizeof (MonoContext));
  74                 }
  75         } else {
  76                 g_assert (!info->client_info.stack_start);
  77         }
  78
  79         /* Notify the JIT */
  80         if (mono_gc_get_gc_callbacks ()->thread_suspend_func)
  81                 mono_gc_get_gc_callbacks ()->thread_suspend_func (info->client_info.runtime_data, context, NULL);
  82
  83         SGEN_LOG (4, "Posting suspend_ack_semaphore for suspend from %p %p", info, (gpointer) (gsize) mono_native_thread_id_get ());
  84
  85         /*
  86         Block the restart signal.
  87         We need to block the restart signal while posting to the suspend_ack semaphore or we race to sigsuspend,
  88         which might miss the signal and get stuck.
  89         */
  90         pthread_sigmask (SIG_BLOCK, &suspend_ack_signal_mask, NULL);
  91
  92         /* notify the waiting thread */
  93         SGEN_SEMAPHORE_POST (suspend_ack_semaphore_ptr);
  94         info->client_info.stop_count = stop_count;
  95
  96         /* wait until we receive the restart signal */
  97         do {
  98                 info->client_info.signal = 0;
  99                 sigsuspend (&suspend_signal_mask);
 100         } while (info->client_info.signal != restart_signal_num);
 101
 102         /* Unblock the restart signal. */
 103         pthread_sigmask (SIG_UNBLOCK, &suspend_ack_signal_mask, NULL);
 104
 105         SGEN_LOG (4, "Posting suspend_ack_semaphore for resume from %p %p\n", info, (gpointer) (gsize) mono_native_thread_id_get ());
 106         /* notify the waiting thread */
 107         SGEN_SEMAPHORE_POST (suspend_ack_semaphore_ptr);
 108 }
 109
 110 /* LOCKING: assumes the GC lock is held (by the stopping thread) */
 111 MONO_SIG_HANDLER_FUNC (static, suspend_handler)
 112 {
 113         /*
 114          * The suspend signal handler potentially uses syscalls that
 115          * can set errno, and it calls functions that use the hazard
 116          * pointer machinery.  Since we're interrupting other code we
 117          * must restore those to the values they had when we
 118          * interrupted.
 119          */
 120         SgenThreadInfo *info;
 121         int old_errno = errno;
 122         int hp_save_index = mono_hazard_pointer_save_for_signal_handler ();
 123         MONO_SIG_HANDLER_GET_CONTEXT;
 124
 125         info = mono_thread_info_current ();
 126         suspend_thread (info, ctx);
 127
 128         mono_hazard_pointer_restore_for_signal_handler (hp_save_index);
 129         errno = old_errno;
 130 }
 131
 132 MONO_SIG_HANDLER_FUNC (static, restart_handler)
 133 {
 134         SgenThreadInfo *info;
 135         int old_errno = errno;
 136
 137         info = mono_thread_info_current ();
 138         info->client_info.signal = restart_signal_num;
 139         SGEN_LOG (4, "Restart handler in %p %p", info, (gpointer) (gsize) mono_native_thread_id_get ());
 140         errno = old_errno;
 141 }
 142
 143 gboolean
 144 sgen_resume_thread (SgenThreadInfo *info)
 145 {
 146         return mono_threads_pthread_kill (info, restart_signal_num) == 0;
 147 }
 148
 149 gboolean
 150 sgen_suspend_thread (SgenThreadInfo *info)
 151 {
 152         return mono_threads_pthread_kill (info, suspend_signal_num) == 0;
 153 }
 154
 155 void
 156 sgen_wait_for_suspend_ack (int count)
 157 {
 158         int i, result;
 159
 160         for (i = 0; i < count; ++i) {
 161                 while ((result = SGEN_SEMAPHORE_WAIT (suspend_ack_semaphore_ptr)) != 0) {
 162                         if (errno != EINTR) {
 163                                 g_error ("SGEN_SEMAPHORE_WAIT FAILED with %d errno %d (%s)", result, errno, strerror (errno));
 164                         }
 165                 }
 166         }
 167 }
 168
 169 int
 170 sgen_thread_handshake (BOOL suspend)
 171 {
 172         int count, result;
 173         int signum = suspend ? suspend_signal_num : restart_signal_num;
 174
 175         MonoNativeThreadId me = mono_native_thread_id_get ();
 176
 177         count = 0;
 178         mono_thread_info_current ()->client_info.suspend_done = TRUE;
 179         FOREACH_THREAD (info) {
 180                 if (mono_native_thread_id_equals (mono_thread_info_get_tid (info), me)) {
 181                         continue;
 182                 }
 183                 info->client_info.suspend_done = FALSE;
 184                 if (info->client_info.gc_disabled)
 185                         continue;
 186                 /*if (signum == suspend_signal_num && info->stop_count == global_stop_count)
 187                         continue;*/
 188                 result = mono_threads_pthread_kill (info, signum);
 189                 if (result == 0) {
 190                         count++;
 191                 } else {
 192                         info->client_info.skip = 1;
 193                 }
 194         } FOREACH_THREAD_END
 195
 196         sgen_wait_for_suspend_ack (count);
 197
 198         SGEN_LOG (4, "%s handshake for %d threads\n", suspend ? "suspend" : "resume", count);
 199
 200         return count;
 201 }
 202
 203 void
 204 sgen_os_init (void)
 205 {
 206         struct sigaction sinfo;
 207
 208         if (mono_thread_info_unified_management_enabled ())
 209                 return;
 210
 211         suspend_ack_semaphore_ptr = &suspend_ack_semaphore;
 212         SGEN_SEMAPHORE_INIT (&suspend_ack_semaphore, 0);
 213
 214         sigfillset (&sinfo.sa_mask);
 215         sinfo.sa_flags = SA_RESTART | SA_SIGINFO;
 216         sinfo.sa_sigaction = suspend_handler;
 217         if (sigaction (suspend_signal_num, &sinfo, NULL) != 0) {
 218                 g_error ("failed sigaction");
 219         }
 220
 221         sinfo.sa_handler = (void (*)(int))restart_handler;
 222         if (sigaction (restart_signal_num, &sinfo, NULL) != 0) {
 223                 g_error ("failed sigaction");
 224         }
 225
 226         sigfillset (&suspend_signal_mask);
 227         sigdelset (&suspend_signal_mask, restart_signal_num);
 228
 229         sigemptyset (&suspend_ack_signal_mask);
 230         sigaddset (&suspend_ack_signal_mask, restart_signal_num);
 231
 232 }
 233
 234 int
 235 mono_gc_get_suspend_signal (void)
 236 {
 237         return suspend_signal_num;
 238 }
 239
 240 int
 241 mono_gc_get_restart_signal (void)
 242 {
 243         return restart_signal_num;
 244 }
 245 #endif
 246 #endif