old-cross-binutils/gdb/testsuite/gdb.threads/step-over-trips-on-watchpoint.exp

125 lines
3.9 KiB
Text
Raw Normal View History

# Copyright (C) 2014-2015 Free Software Foundation, Inc.
Fix for even more missed events; eliminate thread-hop code. Even with deferred_step_ptid out of the way, GDB can still lose watchpoints. If a watchpoint triggers and the PC points to an address where a thread-specific breakpoint for another thread is set, the thread-hop code triggers, and we lose the watchpoint: if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP) { int thread_hop_needed = 0; struct address_space *aspace = get_regcache_aspace (get_thread_regcache (ecs->ptid)); /* Check if a regular breakpoint has been hit before checking for a potential single step breakpoint. Otherwise, GDB will not see this breakpoint hit when stepping onto breakpoints. */ if (regular_breakpoint_inserted_here_p (aspace, stop_pc)) { if (!breakpoint_thread_match (aspace, stop_pc, ecs->ptid)) thread_hop_needed = 1; ^^^^^^^^^^^^^^^^^^^^^ } And on software single-step targets, even without a thread-specific breakpoint in the way, here in the thread-hop code: else if (singlestep_breakpoints_inserted_p) { ... if (!ptid_equal (singlestep_ptid, ecs->ptid) && in_thread_list (singlestep_ptid)) { /* If the PC of the thread we were trying to single-step has changed, discard this event (which we were going to ignore anyway), and pretend we saw that thread trap. This prevents us continuously moving the single-step breakpoint forward, one instruction at a time. If the PC has changed, then the thread we were trying to single-step has trapped or been signalled, but the event has not been reported to GDB yet. There might be some cases where this loses signal information, if a signal has arrived at exactly the same time that the PC changed, but this is the best we can do with the information available. Perhaps we should arrange to report all events for all threads when they stop, or to re-poll the remote looking for this particular thread (i.e. temporarily enable schedlock). */ CORE_ADDR new_singlestep_pc = regcache_read_pc (get_thread_regcache (singlestep_ptid)); if (new_singlestep_pc != singlestep_pc) { enum gdb_signal stop_signal; if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread," " but expected thread advanced also\n"); /* The current context still belongs to singlestep_ptid. Don't swap here, since that's the context we want to use. Just fudge our state and continue. */ stop_signal = ecs->event_thread->suspend.stop_signal; ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0; ecs->ptid = singlestep_ptid; ecs->event_thread = find_thread_ptid (ecs->ptid); ecs->event_thread->suspend.stop_signal = stop_signal; stop_pc = new_singlestep_pc; } else { if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread\n"); thread_hop_needed = 1; stepping_past_singlestep_breakpoint = 1; saved_singlestep_ptid = singlestep_ptid; } } } we either end up with thread_hop_needed, ignoring the watchpoint SIGTRAP, or switch to the stepping thread, again ignoring that the SIGTRAP could be for some other event. The new test added by this patch exercises both paths. So the fix is similar to the deferred_step_ptid fix -- defer the thread hop to _after_ the SIGTRAP had a change of passing through the regular bpstat handling. If the wrong thread hits a breakpoint, we'll just end up with BPSTAT_WHAT_SINGLE, and if nothing causes a stop, keep_going starts a step-over. Most of the stepping_past_singlestep_breakpoint mechanism is really not necessary -- setting the thread to step over a breakpoint with thread->trap_expected is sufficient to keep all other threads locked. It's best to still keep the flag in some form though, because when we get to keep_going, the software single-step breakpoint we need to step over is already gone -- an optimization done by a follow up patch will check whether a step-over is still be necessary by looking to see whether the breakpoint is still there, and would find the thread no longer needs a step-over, while we still want it. Special care is still needed to handle the case of PC of the thread we were trying to single-step having changed, like in the old code. We can't just keep_going and re-step it, as in that case we can over-step the thread (if it was already done with the step, but hasn't reported it yet, we'd ask it to step even further). That's now handled in switch_back_to_stepped_thread. As bonus, we're now using a technique that doesn't lose signals, unlike the old code -- we now insert a breakpoint at PC, and resume, which either reports the breakpoint immediately, or any pending signal. Tested on x86_64 Fedora 17, against pristine mainline, and against a branch that implements software single-step on x86. gdb/ 2014-03-20 Pedro Alves <palves@redhat.com> * breakpoint.c (single_step_breakpoint_inserted_here_p): Make extern. * breakpoint.h (single_step_breakpoint_inserted_here_p): Declare. * infrun.c (saved_singlestep_ptid) (stepping_past_singlestep_breakpoint): Delete. (resume): Remove stepping_past_singlestep_breakpoint handling. (proceed): Store the prev_pc of the stepping thread too. (init_wait_for_inferior): Adjust. Clear singlestep_ptid and singlestep_pc. (enum infwait_states): Delete infwait_thread_hop_state. (struct execution_control_state) <hit_singlestep_breakpoint>: New field. (handle_inferior_event): Adjust. (handle_signal_stop): Delete stepping_past_singlestep_breakpoint handling and the thread-hop code. Before removing single-step breakpoints, check whether the thread hit a single-step breakpoint of another thread. If it did, the trap is not a random signal. (switch_back_to_stepped_thread): If the event thread hit a single-step breakpoint, unblock it before switching to the stepping thread. Handle the case of the stepped thread having advanced already. (keep_going): Handle the case of the current thread moving past a single-step breakpoint. gdb/testsuite/ 2014-03-20 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-trips-on-watchpoint.c: New file. * gdb.threads/step-over-trips-on-watchpoint.exp: New file.
2014-03-20 13:26:32 +00:00
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# Test that when a step-over trips on a watchpoint, that watchpoint is
# reported.
standard_testfile
set executable ${testfile}
# This test verifies that a watchpoint is detected in a multithreaded
# program so the test is only meaningful on a system with hardware
# watchpoints.
if {[skip_hw_watchpoint_tests]} {
return 0
}
if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
executable [list debug "incdir=${objdir}"]] != "" } {
return -1
}
proc do_test { with_bp } {
global executable
Make gdb.threads/step-over-trips-on-watchpoint.exp effective on !x86 This test is currently failing like this on (at least) PPC64 and s390x: FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: step FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: next: next FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: with thread-specific bp: step: step FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: with thread-specific bp: next: next gdb.log: (gdb) PASS: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: set scheduler-locking off step wait_threads () at ../../../src/gdb/testsuite/gdb.threads/step-over-trips-on-watchpoint.c:49 49 return 1; /* in wait_threads */ (gdb) FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: step The problem is that the test assumes that both the "watch_me = 1;" and the "other = 1;" lines compile to a single instruction each, which happens to be true on x86, but no necessarily true everywhere else. The result is that the test doesn't really test what it wants to test. Fix it by looking for the instruction that triggers the watchpoint. gdb/ChangeLog: 2015-04-10 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-trips-on-watchpoint.c (child_function): Remove comment. * gdb.threads/step-over-trips-on-watchpoint.exp (do_test): Find both the address of the instruction that triggers the watchpoint and the address of the instruction immediately after, and use those addresses for the test. Fix comment.
2015-04-10 12:11:32 +00:00
global gdb_prompt
global hex
Fix for even more missed events; eliminate thread-hop code. Even with deferred_step_ptid out of the way, GDB can still lose watchpoints. If a watchpoint triggers and the PC points to an address where a thread-specific breakpoint for another thread is set, the thread-hop code triggers, and we lose the watchpoint: if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP) { int thread_hop_needed = 0; struct address_space *aspace = get_regcache_aspace (get_thread_regcache (ecs->ptid)); /* Check if a regular breakpoint has been hit before checking for a potential single step breakpoint. Otherwise, GDB will not see this breakpoint hit when stepping onto breakpoints. */ if (regular_breakpoint_inserted_here_p (aspace, stop_pc)) { if (!breakpoint_thread_match (aspace, stop_pc, ecs->ptid)) thread_hop_needed = 1; ^^^^^^^^^^^^^^^^^^^^^ } And on software single-step targets, even without a thread-specific breakpoint in the way, here in the thread-hop code: else if (singlestep_breakpoints_inserted_p) { ... if (!ptid_equal (singlestep_ptid, ecs->ptid) && in_thread_list (singlestep_ptid)) { /* If the PC of the thread we were trying to single-step has changed, discard this event (which we were going to ignore anyway), and pretend we saw that thread trap. This prevents us continuously moving the single-step breakpoint forward, one instruction at a time. If the PC has changed, then the thread we were trying to single-step has trapped or been signalled, but the event has not been reported to GDB yet. There might be some cases where this loses signal information, if a signal has arrived at exactly the same time that the PC changed, but this is the best we can do with the information available. Perhaps we should arrange to report all events for all threads when they stop, or to re-poll the remote looking for this particular thread (i.e. temporarily enable schedlock). */ CORE_ADDR new_singlestep_pc = regcache_read_pc (get_thread_regcache (singlestep_ptid)); if (new_singlestep_pc != singlestep_pc) { enum gdb_signal stop_signal; if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread," " but expected thread advanced also\n"); /* The current context still belongs to singlestep_ptid. Don't swap here, since that's the context we want to use. Just fudge our state and continue. */ stop_signal = ecs->event_thread->suspend.stop_signal; ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0; ecs->ptid = singlestep_ptid; ecs->event_thread = find_thread_ptid (ecs->ptid); ecs->event_thread->suspend.stop_signal = stop_signal; stop_pc = new_singlestep_pc; } else { if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread\n"); thread_hop_needed = 1; stepping_past_singlestep_breakpoint = 1; saved_singlestep_ptid = singlestep_ptid; } } } we either end up with thread_hop_needed, ignoring the watchpoint SIGTRAP, or switch to the stepping thread, again ignoring that the SIGTRAP could be for some other event. The new test added by this patch exercises both paths. So the fix is similar to the deferred_step_ptid fix -- defer the thread hop to _after_ the SIGTRAP had a change of passing through the regular bpstat handling. If the wrong thread hits a breakpoint, we'll just end up with BPSTAT_WHAT_SINGLE, and if nothing causes a stop, keep_going starts a step-over. Most of the stepping_past_singlestep_breakpoint mechanism is really not necessary -- setting the thread to step over a breakpoint with thread->trap_expected is sufficient to keep all other threads locked. It's best to still keep the flag in some form though, because when we get to keep_going, the software single-step breakpoint we need to step over is already gone -- an optimization done by a follow up patch will check whether a step-over is still be necessary by looking to see whether the breakpoint is still there, and would find the thread no longer needs a step-over, while we still want it. Special care is still needed to handle the case of PC of the thread we were trying to single-step having changed, like in the old code. We can't just keep_going and re-step it, as in that case we can over-step the thread (if it was already done with the step, but hasn't reported it yet, we'd ask it to step even further). That's now handled in switch_back_to_stepped_thread. As bonus, we're now using a technique that doesn't lose signals, unlike the old code -- we now insert a breakpoint at PC, and resume, which either reports the breakpoint immediately, or any pending signal. Tested on x86_64 Fedora 17, against pristine mainline, and against a branch that implements software single-step on x86. gdb/ 2014-03-20 Pedro Alves <palves@redhat.com> * breakpoint.c (single_step_breakpoint_inserted_here_p): Make extern. * breakpoint.h (single_step_breakpoint_inserted_here_p): Declare. * infrun.c (saved_singlestep_ptid) (stepping_past_singlestep_breakpoint): Delete. (resume): Remove stepping_past_singlestep_breakpoint handling. (proceed): Store the prev_pc of the stepping thread too. (init_wait_for_inferior): Adjust. Clear singlestep_ptid and singlestep_pc. (enum infwait_states): Delete infwait_thread_hop_state. (struct execution_control_state) <hit_singlestep_breakpoint>: New field. (handle_inferior_event): Adjust. (handle_signal_stop): Delete stepping_past_singlestep_breakpoint handling and the thread-hop code. Before removing single-step breakpoints, check whether the thread hit a single-step breakpoint of another thread. If it did, the trap is not a random signal. (switch_back_to_stepped_thread): If the event thread hit a single-step breakpoint, unblock it before switching to the stepping thread. Handle the case of the stepped thread having advanced already. (keep_going): Handle the case of the current thread moving past a single-step breakpoint. gdb/testsuite/ 2014-03-20 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-trips-on-watchpoint.c: New file. * gdb.threads/step-over-trips-on-watchpoint.exp: New file.
2014-03-20 13:26:32 +00:00
if ${with_bp} {
set prefix "with thread-specific bp"
} else {
set prefix "no thread-specific bp"
}
with_test_prefix $prefix {
# Cover both stepping and non-stepping execution commands.
foreach command {"step" "next" "continue" } {
with_test_prefix $command {
clean_restart $executable
if ![runto_main] {
continue
}
gdb_breakpoint [gdb_get_line_number "set wait-thread breakpoint here"]
gdb_continue_to_breakpoint "run to wait-thread breakpoint"
gdb_test "info threads" "2 .*\\\* 1.*" "info threads shows all threads"
gdb_test_no_output "set scheduler-locking on"
delete_breakpoints
gdb_breakpoint [gdb_get_line_number "set breakpoint child here"]
gdb_test "thread 2" "Switching to .*"
gdb_continue_to_breakpoint "run to breakpoint in thread 2"
Make gdb.threads/step-over-trips-on-watchpoint.exp effective on !x86 This test is currently failing like this on (at least) PPC64 and s390x: FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: step FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: next: next FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: with thread-specific bp: step: step FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: with thread-specific bp: next: next gdb.log: (gdb) PASS: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: set scheduler-locking off step wait_threads () at ../../../src/gdb/testsuite/gdb.threads/step-over-trips-on-watchpoint.c:49 49 return 1; /* in wait_threads */ (gdb) FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: step The problem is that the test assumes that both the "watch_me = 1;" and the "other = 1;" lines compile to a single instruction each, which happens to be true on x86, but no necessarily true everywhere else. The result is that the test doesn't really test what it wants to test. Fix it by looking for the instruction that triggers the watchpoint. gdb/ChangeLog: 2015-04-10 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-trips-on-watchpoint.c (child_function): Remove comment. * gdb.threads/step-over-trips-on-watchpoint.exp (do_test): Find both the address of the instruction that triggers the watchpoint and the address of the instruction immediately after, and use those addresses for the test. Fix comment.
2015-04-10 12:11:32 +00:00
set address_triggers_watch "<invalid>"
set after_address_triggers_watch "<invalid>"
# Let the watchpoint trigger once (with the other
# thread locked), in order to find both the address of
# the instruction that triggers the watchpoint and the
# address of the instruction immediately after.
with_test_prefix "find addresses" {
gdb_test "p watch_me = 0" " = 0" "clear watch_me"
gdb_test "watch watch_me" "Hardware watchpoint .*"
gdb_test "continue" \
"Hardware watchpoint.*: watch_me.*New value = 1.*" \
"continue to watchpoint"
set msg "find addresses"
gdb_test_multiple "disassemble" $msg {
-re " ($hex) \[^\r\n\]*\r\n=> ($hex) .*$gdb_prompt $" {
set address_triggers_watch $expect_out(1,string)
set after_address_triggers_watch $expect_out(2,string)
pass $msg
}
}
delete_breakpoints
}
gdb_breakpoint "*$address_triggers_watch"
gdb_continue_to_breakpoint \
"run to instruction that triggers watch in thread 2"
Fix for even more missed events; eliminate thread-hop code. Even with deferred_step_ptid out of the way, GDB can still lose watchpoints. If a watchpoint triggers and the PC points to an address where a thread-specific breakpoint for another thread is set, the thread-hop code triggers, and we lose the watchpoint: if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP) { int thread_hop_needed = 0; struct address_space *aspace = get_regcache_aspace (get_thread_regcache (ecs->ptid)); /* Check if a regular breakpoint has been hit before checking for a potential single step breakpoint. Otherwise, GDB will not see this breakpoint hit when stepping onto breakpoints. */ if (regular_breakpoint_inserted_here_p (aspace, stop_pc)) { if (!breakpoint_thread_match (aspace, stop_pc, ecs->ptid)) thread_hop_needed = 1; ^^^^^^^^^^^^^^^^^^^^^ } And on software single-step targets, even without a thread-specific breakpoint in the way, here in the thread-hop code: else if (singlestep_breakpoints_inserted_p) { ... if (!ptid_equal (singlestep_ptid, ecs->ptid) && in_thread_list (singlestep_ptid)) { /* If the PC of the thread we were trying to single-step has changed, discard this event (which we were going to ignore anyway), and pretend we saw that thread trap. This prevents us continuously moving the single-step breakpoint forward, one instruction at a time. If the PC has changed, then the thread we were trying to single-step has trapped or been signalled, but the event has not been reported to GDB yet. There might be some cases where this loses signal information, if a signal has arrived at exactly the same time that the PC changed, but this is the best we can do with the information available. Perhaps we should arrange to report all events for all threads when they stop, or to re-poll the remote looking for this particular thread (i.e. temporarily enable schedlock). */ CORE_ADDR new_singlestep_pc = regcache_read_pc (get_thread_regcache (singlestep_ptid)); if (new_singlestep_pc != singlestep_pc) { enum gdb_signal stop_signal; if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread," " but expected thread advanced also\n"); /* The current context still belongs to singlestep_ptid. Don't swap here, since that's the context we want to use. Just fudge our state and continue. */ stop_signal = ecs->event_thread->suspend.stop_signal; ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0; ecs->ptid = singlestep_ptid; ecs->event_thread = find_thread_ptid (ecs->ptid); ecs->event_thread->suspend.stop_signal = stop_signal; stop_pc = new_singlestep_pc; } else { if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread\n"); thread_hop_needed = 1; stepping_past_singlestep_breakpoint = 1; saved_singlestep_ptid = singlestep_ptid; } } } we either end up with thread_hop_needed, ignoring the watchpoint SIGTRAP, or switch to the stepping thread, again ignoring that the SIGTRAP could be for some other event. The new test added by this patch exercises both paths. So the fix is similar to the deferred_step_ptid fix -- defer the thread hop to _after_ the SIGTRAP had a change of passing through the regular bpstat handling. If the wrong thread hits a breakpoint, we'll just end up with BPSTAT_WHAT_SINGLE, and if nothing causes a stop, keep_going starts a step-over. Most of the stepping_past_singlestep_breakpoint mechanism is really not necessary -- setting the thread to step over a breakpoint with thread->trap_expected is sufficient to keep all other threads locked. It's best to still keep the flag in some form though, because when we get to keep_going, the software single-step breakpoint we need to step over is already gone -- an optimization done by a follow up patch will check whether a step-over is still be necessary by looking to see whether the breakpoint is still there, and would find the thread no longer needs a step-over, while we still want it. Special care is still needed to handle the case of PC of the thread we were trying to single-step having changed, like in the old code. We can't just keep_going and re-step it, as in that case we can over-step the thread (if it was already done with the step, but hasn't reported it yet, we'd ask it to step even further). That's now handled in switch_back_to_stepped_thread. As bonus, we're now using a technique that doesn't lose signals, unlike the old code -- we now insert a breakpoint at PC, and resume, which either reports the breakpoint immediately, or any pending signal. Tested on x86_64 Fedora 17, against pristine mainline, and against a branch that implements software single-step on x86. gdb/ 2014-03-20 Pedro Alves <palves@redhat.com> * breakpoint.c (single_step_breakpoint_inserted_here_p): Make extern. * breakpoint.h (single_step_breakpoint_inserted_here_p): Declare. * infrun.c (saved_singlestep_ptid) (stepping_past_singlestep_breakpoint): Delete. (resume): Remove stepping_past_singlestep_breakpoint handling. (proceed): Store the prev_pc of the stepping thread too. (init_wait_for_inferior): Adjust. Clear singlestep_ptid and singlestep_pc. (enum infwait_states): Delete infwait_thread_hop_state. (struct execution_control_state) <hit_singlestep_breakpoint>: New field. (handle_inferior_event): Adjust. (handle_signal_stop): Delete stepping_past_singlestep_breakpoint handling and the thread-hop code. Before removing single-step breakpoints, check whether the thread hit a single-step breakpoint of another thread. If it did, the trap is not a random signal. (switch_back_to_stepped_thread): If the event thread hit a single-step breakpoint, unblock it before switching to the stepping thread. Handle the case of the stepped thread having advanced already. (keep_going): Handle the case of the current thread moving past a single-step breakpoint. gdb/testsuite/ 2014-03-20 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-trips-on-watchpoint.c: New file. * gdb.threads/step-over-trips-on-watchpoint.exp: New file.
2014-03-20 13:26:32 +00:00
gdb_test "p counter = 0" " = 0" "unbreak loop in thread 2"
gdb_test "p watch_me = 0" " = 0" "clear watch_me"
gdb_test "watch watch_me" "Hardware watchpoint .*"
if ${with_bp} {
# Set a thread-specific breakpoint (for the wrong
# thread) right after instruction that triggers
# the watchpoint.
Make gdb.threads/step-over-trips-on-watchpoint.exp effective on !x86 This test is currently failing like this on (at least) PPC64 and s390x: FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: step FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: next: next FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: with thread-specific bp: step: step FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: with thread-specific bp: next: next gdb.log: (gdb) PASS: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: set scheduler-locking off step wait_threads () at ../../../src/gdb/testsuite/gdb.threads/step-over-trips-on-watchpoint.c:49 49 return 1; /* in wait_threads */ (gdb) FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: step The problem is that the test assumes that both the "watch_me = 1;" and the "other = 1;" lines compile to a single instruction each, which happens to be true on x86, but no necessarily true everywhere else. The result is that the test doesn't really test what it wants to test. Fix it by looking for the instruction that triggers the watchpoint. gdb/ChangeLog: 2015-04-10 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-trips-on-watchpoint.c (child_function): Remove comment. * gdb.threads/step-over-trips-on-watchpoint.exp (do_test): Find both the address of the instruction that triggers the watchpoint and the address of the instruction immediately after, and use those addresses for the test. Fix comment.
2015-04-10 12:11:32 +00:00
gdb_test "b *$after_address_triggers_watch thread 1"
Fix for even more missed events; eliminate thread-hop code. Even with deferred_step_ptid out of the way, GDB can still lose watchpoints. If a watchpoint triggers and the PC points to an address where a thread-specific breakpoint for another thread is set, the thread-hop code triggers, and we lose the watchpoint: if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP) { int thread_hop_needed = 0; struct address_space *aspace = get_regcache_aspace (get_thread_regcache (ecs->ptid)); /* Check if a regular breakpoint has been hit before checking for a potential single step breakpoint. Otherwise, GDB will not see this breakpoint hit when stepping onto breakpoints. */ if (regular_breakpoint_inserted_here_p (aspace, stop_pc)) { if (!breakpoint_thread_match (aspace, stop_pc, ecs->ptid)) thread_hop_needed = 1; ^^^^^^^^^^^^^^^^^^^^^ } And on software single-step targets, even without a thread-specific breakpoint in the way, here in the thread-hop code: else if (singlestep_breakpoints_inserted_p) { ... if (!ptid_equal (singlestep_ptid, ecs->ptid) && in_thread_list (singlestep_ptid)) { /* If the PC of the thread we were trying to single-step has changed, discard this event (which we were going to ignore anyway), and pretend we saw that thread trap. This prevents us continuously moving the single-step breakpoint forward, one instruction at a time. If the PC has changed, then the thread we were trying to single-step has trapped or been signalled, but the event has not been reported to GDB yet. There might be some cases where this loses signal information, if a signal has arrived at exactly the same time that the PC changed, but this is the best we can do with the information available. Perhaps we should arrange to report all events for all threads when they stop, or to re-poll the remote looking for this particular thread (i.e. temporarily enable schedlock). */ CORE_ADDR new_singlestep_pc = regcache_read_pc (get_thread_regcache (singlestep_ptid)); if (new_singlestep_pc != singlestep_pc) { enum gdb_signal stop_signal; if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread," " but expected thread advanced also\n"); /* The current context still belongs to singlestep_ptid. Don't swap here, since that's the context we want to use. Just fudge our state and continue. */ stop_signal = ecs->event_thread->suspend.stop_signal; ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0; ecs->ptid = singlestep_ptid; ecs->event_thread = find_thread_ptid (ecs->ptid); ecs->event_thread->suspend.stop_signal = stop_signal; stop_pc = new_singlestep_pc; } else { if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread\n"); thread_hop_needed = 1; stepping_past_singlestep_breakpoint = 1; saved_singlestep_ptid = singlestep_ptid; } } } we either end up with thread_hop_needed, ignoring the watchpoint SIGTRAP, or switch to the stepping thread, again ignoring that the SIGTRAP could be for some other event. The new test added by this patch exercises both paths. So the fix is similar to the deferred_step_ptid fix -- defer the thread hop to _after_ the SIGTRAP had a change of passing through the regular bpstat handling. If the wrong thread hits a breakpoint, we'll just end up with BPSTAT_WHAT_SINGLE, and if nothing causes a stop, keep_going starts a step-over. Most of the stepping_past_singlestep_breakpoint mechanism is really not necessary -- setting the thread to step over a breakpoint with thread->trap_expected is sufficient to keep all other threads locked. It's best to still keep the flag in some form though, because when we get to keep_going, the software single-step breakpoint we need to step over is already gone -- an optimization done by a follow up patch will check whether a step-over is still be necessary by looking to see whether the breakpoint is still there, and would find the thread no longer needs a step-over, while we still want it. Special care is still needed to handle the case of PC of the thread we were trying to single-step having changed, like in the old code. We can't just keep_going and re-step it, as in that case we can over-step the thread (if it was already done with the step, but hasn't reported it yet, we'd ask it to step even further). That's now handled in switch_back_to_stepped_thread. As bonus, we're now using a technique that doesn't lose signals, unlike the old code -- we now insert a breakpoint at PC, and resume, which either reports the breakpoint immediately, or any pending signal. Tested on x86_64 Fedora 17, against pristine mainline, and against a branch that implements software single-step on x86. gdb/ 2014-03-20 Pedro Alves <palves@redhat.com> * breakpoint.c (single_step_breakpoint_inserted_here_p): Make extern. * breakpoint.h (single_step_breakpoint_inserted_here_p): Declare. * infrun.c (saved_singlestep_ptid) (stepping_past_singlestep_breakpoint): Delete. (resume): Remove stepping_past_singlestep_breakpoint handling. (proceed): Store the prev_pc of the stepping thread too. (init_wait_for_inferior): Adjust. Clear singlestep_ptid and singlestep_pc. (enum infwait_states): Delete infwait_thread_hop_state. (struct execution_control_state) <hit_singlestep_breakpoint>: New field. (handle_inferior_event): Adjust. (handle_signal_stop): Delete stepping_past_singlestep_breakpoint handling and the thread-hop code. Before removing single-step breakpoints, check whether the thread hit a single-step breakpoint of another thread. If it did, the trap is not a random signal. (switch_back_to_stepped_thread): If the event thread hit a single-step breakpoint, unblock it before switching to the stepping thread. Handle the case of the stepped thread having advanced already. (keep_going): Handle the case of the current thread moving past a single-step breakpoint. gdb/testsuite/ 2014-03-20 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-trips-on-watchpoint.c: New file. * gdb.threads/step-over-trips-on-watchpoint.exp: New file.
2014-03-20 13:26:32 +00:00
}
# Switch back to thread 1 and disable scheduler locking.
gdb_test "thread 1" "Switching to .*"
gdb_test_no_output "set scheduler-locking off"
# Thread 2 is still stopped at a breakpoint that needs to be
Make gdb.threads/step-over-trips-on-watchpoint.exp effective on !x86 This test is currently failing like this on (at least) PPC64 and s390x: FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: step FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: next: next FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: with thread-specific bp: step: step FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: with thread-specific bp: next: next gdb.log: (gdb) PASS: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: set scheduler-locking off step wait_threads () at ../../../src/gdb/testsuite/gdb.threads/step-over-trips-on-watchpoint.c:49 49 return 1; /* in wait_threads */ (gdb) FAIL: gdb.threads/step-over-trips-on-watchpoint.exp: no thread-specific bp: step: step The problem is that the test assumes that both the "watch_me = 1;" and the "other = 1;" lines compile to a single instruction each, which happens to be true on x86, but no necessarily true everywhere else. The result is that the test doesn't really test what it wants to test. Fix it by looking for the instruction that triggers the watchpoint. gdb/ChangeLog: 2015-04-10 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-trips-on-watchpoint.c (child_function): Remove comment. * gdb.threads/step-over-trips-on-watchpoint.exp (do_test): Find both the address of the instruction that triggers the watchpoint and the address of the instruction immediately after, and use those addresses for the test. Fix comment.
2015-04-10 12:11:32 +00:00
# stepped over before proceeding thread 1. However, the
# instruction that is under the breakpoint triggers a
# watchpoint, which should trap and be reported to the
# user.
Fix for even more missed events; eliminate thread-hop code. Even with deferred_step_ptid out of the way, GDB can still lose watchpoints. If a watchpoint triggers and the PC points to an address where a thread-specific breakpoint for another thread is set, the thread-hop code triggers, and we lose the watchpoint: if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP) { int thread_hop_needed = 0; struct address_space *aspace = get_regcache_aspace (get_thread_regcache (ecs->ptid)); /* Check if a regular breakpoint has been hit before checking for a potential single step breakpoint. Otherwise, GDB will not see this breakpoint hit when stepping onto breakpoints. */ if (regular_breakpoint_inserted_here_p (aspace, stop_pc)) { if (!breakpoint_thread_match (aspace, stop_pc, ecs->ptid)) thread_hop_needed = 1; ^^^^^^^^^^^^^^^^^^^^^ } And on software single-step targets, even without a thread-specific breakpoint in the way, here in the thread-hop code: else if (singlestep_breakpoints_inserted_p) { ... if (!ptid_equal (singlestep_ptid, ecs->ptid) && in_thread_list (singlestep_ptid)) { /* If the PC of the thread we were trying to single-step has changed, discard this event (which we were going to ignore anyway), and pretend we saw that thread trap. This prevents us continuously moving the single-step breakpoint forward, one instruction at a time. If the PC has changed, then the thread we were trying to single-step has trapped or been signalled, but the event has not been reported to GDB yet. There might be some cases where this loses signal information, if a signal has arrived at exactly the same time that the PC changed, but this is the best we can do with the information available. Perhaps we should arrange to report all events for all threads when they stop, or to re-poll the remote looking for this particular thread (i.e. temporarily enable schedlock). */ CORE_ADDR new_singlestep_pc = regcache_read_pc (get_thread_regcache (singlestep_ptid)); if (new_singlestep_pc != singlestep_pc) { enum gdb_signal stop_signal; if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread," " but expected thread advanced also\n"); /* The current context still belongs to singlestep_ptid. Don't swap here, since that's the context we want to use. Just fudge our state and continue. */ stop_signal = ecs->event_thread->suspend.stop_signal; ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0; ecs->ptid = singlestep_ptid; ecs->event_thread = find_thread_ptid (ecs->ptid); ecs->event_thread->suspend.stop_signal = stop_signal; stop_pc = new_singlestep_pc; } else { if (debug_infrun) fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread\n"); thread_hop_needed = 1; stepping_past_singlestep_breakpoint = 1; saved_singlestep_ptid = singlestep_ptid; } } } we either end up with thread_hop_needed, ignoring the watchpoint SIGTRAP, or switch to the stepping thread, again ignoring that the SIGTRAP could be for some other event. The new test added by this patch exercises both paths. So the fix is similar to the deferred_step_ptid fix -- defer the thread hop to _after_ the SIGTRAP had a change of passing through the regular bpstat handling. If the wrong thread hits a breakpoint, we'll just end up with BPSTAT_WHAT_SINGLE, and if nothing causes a stop, keep_going starts a step-over. Most of the stepping_past_singlestep_breakpoint mechanism is really not necessary -- setting the thread to step over a breakpoint with thread->trap_expected is sufficient to keep all other threads locked. It's best to still keep the flag in some form though, because when we get to keep_going, the software single-step breakpoint we need to step over is already gone -- an optimization done by a follow up patch will check whether a step-over is still be necessary by looking to see whether the breakpoint is still there, and would find the thread no longer needs a step-over, while we still want it. Special care is still needed to handle the case of PC of the thread we were trying to single-step having changed, like in the old code. We can't just keep_going and re-step it, as in that case we can over-step the thread (if it was already done with the step, but hasn't reported it yet, we'd ask it to step even further). That's now handled in switch_back_to_stepped_thread. As bonus, we're now using a technique that doesn't lose signals, unlike the old code -- we now insert a breakpoint at PC, and resume, which either reports the breakpoint immediately, or any pending signal. Tested on x86_64 Fedora 17, against pristine mainline, and against a branch that implements software single-step on x86. gdb/ 2014-03-20 Pedro Alves <palves@redhat.com> * breakpoint.c (single_step_breakpoint_inserted_here_p): Make extern. * breakpoint.h (single_step_breakpoint_inserted_here_p): Declare. * infrun.c (saved_singlestep_ptid) (stepping_past_singlestep_breakpoint): Delete. (resume): Remove stepping_past_singlestep_breakpoint handling. (proceed): Store the prev_pc of the stepping thread too. (init_wait_for_inferior): Adjust. Clear singlestep_ptid and singlestep_pc. (enum infwait_states): Delete infwait_thread_hop_state. (struct execution_control_state) <hit_singlestep_breakpoint>: New field. (handle_inferior_event): Adjust. (handle_signal_stop): Delete stepping_past_singlestep_breakpoint handling and the thread-hop code. Before removing single-step breakpoints, check whether the thread hit a single-step breakpoint of another thread. If it did, the trap is not a random signal. (switch_back_to_stepped_thread): If the event thread hit a single-step breakpoint, unblock it before switching to the stepping thread. Handle the case of the stepped thread having advanced already. (keep_going): Handle the case of the current thread moving past a single-step breakpoint. gdb/testsuite/ 2014-03-20 Pedro Alves <palves@redhat.com> * gdb.threads/step-over-trips-on-watchpoint.c: New file. * gdb.threads/step-over-trips-on-watchpoint.exp: New file.
2014-03-20 13:26:32 +00:00
gdb_test "$command" "Hardware watchpoint.*: watch_me.*New value = 1.*"
}
}
}
}
do_test 0
do_test 1