Thu, 26 Mar 2009 14:31:45 -0700
6822204: volatile fences should prefer lock:addl to actual mfence instructions
Reviewed-by: kvn, phh
1 /*
2 * Copyright 2003-2008 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 #include "incls/_precompiled.incl"
26 #include "incls/_thread_solaris_sparc.cpp.incl"
28 // For Forte Analyzer AsyncGetCallTrace profiling support - thread is
29 // currently interrupted by SIGPROF
30 //
31 // NOTE: On Solaris, register windows are flushed in the signal handler
32 // except for possibly the top frame.
33 //
34 bool JavaThread::pd_get_top_frame_for_signal_handler(frame* fr_addr,
35 void* ucontext, bool isInJava) {
37 assert(Thread::current() == this, "caller must be current thread");
38 assert(this->is_Java_thread(), "must be JavaThread");
40 JavaThread* jt = (JavaThread *)this;
42 if (!isInJava) {
43 // make_walkable flushes register windows and grabs last_Java_pc
44 // which can not be done if the ucontext sp matches last_Java_sp
45 // stack walking utilities assume last_Java_pc set if marked flushed
46 jt->frame_anchor()->make_walkable(jt);
47 }
49 // If we have a walkable last_Java_frame, then we should use it
50 // even if isInJava == true. It should be more reliable than
51 // ucontext info.
52 if (jt->has_last_Java_frame() && jt->frame_anchor()->walkable()) {
53 *fr_addr = jt->pd_last_frame();
54 return true;
55 }
57 ucontext_t* uc = (ucontext_t*) ucontext;
59 // At this point, we don't have a walkable last_Java_frame, so
60 // we try to glean some information out of the ucontext.
61 intptr_t* ret_sp;
62 ExtendedPC addr = os::Solaris::fetch_frame_from_ucontext(this, uc,
63 &ret_sp, NULL /* ret_fp only used on Solaris X86 */);
64 if (addr.pc() == NULL || ret_sp == NULL) {
65 // ucontext wasn't useful
66 return false;
67 }
69 frame ret_frame(ret_sp, frame::unpatchable, addr.pc());
71 // we were running Java code when SIGPROF came in
72 if (isInJava) {
75 // If the frame we got is safe then it is most certainly valid
76 if (ret_frame.safe_for_sender(jt)) {
77 *fr_addr = ret_frame;
78 return true;
79 }
81 // If it isn't safe then we can try several things to try and get
82 // a good starting point.
83 //
84 // On sparc the frames are almost certainly walkable in the sense
85 // of sp/fp linkages. However because of recycling of windows if
86 // a piece of code does multiple save's where the initial save creates
87 // a real frame with a return pc and the succeeding save's are used to
88 // simply get free registers and have no real pc then the pc linkage on these
89 // "inner" temporary frames will be bogus.
90 // Since there is in general only a nesting level like
91 // this one deep in general we'll try and unwind such an "inner" frame
92 // here ourselves and see if it makes sense
94 frame unwind_frame(ret_frame.fp(), frame::unpatchable, addr.pc());
96 if (unwind_frame.safe_for_sender(jt)) {
97 *fr_addr = unwind_frame;
98 return true;
99 }
101 // Well that didn't work. Most likely we're toast on this tick
102 // The previous code would try this. I think it is dubious in light
103 // of changes to safe_for_sender and the unwind trick above but
104 // if it gets us a safe frame who wants to argue.
106 // If we have a last_Java_sp, then the SIGPROF signal caught us
107 // right when we were transitioning from _thread_in_Java to a new
108 // JavaThreadState. We use last_Java_sp instead of the sp from
109 // the ucontext since it should be more reliable.
111 if (jt->has_last_Java_frame()) {
112 ret_sp = jt->last_Java_sp();
113 frame ret_frame2(ret_sp, frame::unpatchable, addr.pc());
114 if (ret_frame2.safe_for_sender(jt)) {
115 *fr_addr = ret_frame2;
116 return true;
117 }
118 }
120 // This is the best we can do. We will only be able to decode the top frame
122 *fr_addr = ret_frame;
123 return true;
124 }
126 // At this point, we know we weren't running Java code. We might
127 // have a last_Java_sp, but we don't have a walkable frame.
128 // However, we might still be able to construct something useful
129 // if the thread was running native code.
130 if (jt->has_last_Java_frame()) {
131 assert(!jt->frame_anchor()->walkable(), "case covered above");
133 frame ret_frame(jt->last_Java_sp(), frame::unpatchable, addr.pc());
134 *fr_addr = ret_frame;
135 return true;
136 }
138 // nothing else to try but what we found initially
140 *fr_addr = ret_frame;
141 return true;
142 }