s390x-codegen.h - Define s390_SP and s390_BP

sgen-major-copy-object.h - Correct assertion test sgen-os-posix.c - Prevent race condition between restarting and suspending a thread
gary-b · Apr 2, 2012 · 903bf1f · 903bf1f
1 parent 10cf23f
commit 903bf1f
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Showing 3 changed files with 28 additions and 2 deletions.
diff --git a/mono/arch/s390x/s390x-codegen.h b/mono/arch/s390x/s390x-codegen.h
@@ -146,6 +146,8 @@ typedef enum {
 #define s390_is_uimm12(val)		((glong)val >= 0 && (glong)val <= 4095)
 
 #define STK_BASE			s390_r15
+#define S390_SP				s390_r15
+#define S390_FP				s390_r11
 #define S390_MINIMAL_STACK_SIZE		160
 #define S390_REG_SAVE_OFFSET 		48
 #define S390_PARM_SAVE_OFFSET 		16

diff --git a/mono/metadata/sgen-major-copy-object.h b/mono/metadata/sgen-major-copy-object.h
@@ -154,7 +154,7 @@ nopar_copy_object (void **obj_slot, SgenGrayQueue *queue)
 	 */
 
 	if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
-		DEBUG (9, g_assert (((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr));
+		DEBUG (9, g_assert ((*(MonoVTable**)SGEN_LOAD_VTABLE(obj))->gc_descr));
 		DEBUG (9, fprintf (gc_debug_file, " (already forwarded to %p)\n", forwarded));
 		HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
 		*obj_slot = forwarded;

diff --git a/mono/metadata/sgen-os-posix.c b/mono/metadata/sgen-os-posix.c
@@ -51,6 +51,7 @@ static MonoSemType suspend_ack_semaphore;
 static MonoSemType *suspend_ack_semaphore_ptr;
 
 static sigset_t suspend_signal_mask;
+static sigset_t suspend_ack_signal_mask;
 
 static void
 suspend_thread (SgenThreadInfo *info, void *context)
@@ -104,6 +105,14 @@ suspend_thread (SgenThreadInfo *info, void *context)
 		mono_gc_get_gc_callbacks ()->thread_suspend_func (info->runtime_data, context);
 
 	DEBUG (4, fprintf (gc_debug_file, "Posting suspend_ack_semaphore for suspend from %p %p\n", info, (gpointer)mono_native_thread_id_get ()));
+
+	/*
+	Block the restart signal. 
+	We need to block the restart signal while posting to the suspend_ack semaphore or we race to sigsuspend,
+	which might miss the signal and get stuck.
+	*/
+	pthread_sigmask (SIG_BLOCK, &suspend_ack_signal_mask, NULL);
+
 	/* notify the waiting thread */
 	MONO_SEM_POST (suspend_ack_semaphore_ptr);
 	info->stop_count = stop_count;
@@ -114,6 +123,9 @@ suspend_thread (SgenThreadInfo *info, void *context)
 		sigsuspend (&suspend_signal_mask);
 	} while (info->signal != restart_signal_num && info->doing_handshake);
 
+	/* Unblock the restart signal. */
+	pthread_sigmask (SIG_UNBLOCK, &suspend_ack_signal_mask, NULL);
+
 	DEBUG (4, fprintf (gc_debug_file, "Posting suspend_ack_semaphore for resume from %p %p\n", info, (gpointer)mono_native_thread_id_get ()));
 	/* notify the waiting thread */
 	MONO_SEM_POST (suspend_ack_semaphore_ptr);
@@ -145,6 +157,15 @@ restart_handler (int sig)
 	int old_errno = errno;
 
 	info = mono_thread_info_current ();
+	/*
+	If the thread info is null is means we're currently in the process of cleaning up,
+	the pthread destructor has already kicked in and it has explicitly invoked the suspend handler.
+	
+	This means this thread has been suspended, TLS is dead, so the only option we have is to
+	rely on pthread_self () and seatch over the thread list.
+	*/
+	if (!info)
+		info = mono_thread_info_lookup (pthread_self ());
 
 	/*
 	 * If a thread is dying there might be no thread info.  In
@@ -154,7 +175,6 @@ restart_handler (int sig)
 		info->signal = restart_signal_num;
 		DEBUG (4, fprintf (gc_debug_file, "Restart handler in %p %p\n", info, (gpointer)mono_native_thread_id_get ()));
 	}
-
 	errno = old_errno;
 }
 
@@ -254,6 +274,10 @@ mono_sgen_os_init (void)
 
 	sigfillset (&suspend_signal_mask);
 	sigdelset (&suspend_signal_mask, restart_signal_num);
+
+	sigemptyset (&suspend_ack_signal_mask);
+	sigaddset (&suspend_ack_signal_mask, restart_signal_num);
+
 }
 
 int