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exists_non_stop_target: Avoid flushing frames

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A following patch adds an exists_non_stop_target call in the
target_terminal routines, and that surprisingly caused a weird
regression / GDB crash:

 $ make check RUNTESTFLAGS="--target_board=native-extended-gdbserver" TESTS="gdb.base/signest.exp"
 ...
 configuring for gdbserver local testing (extended-remote)
 Using src/gdb/testsuite/config/extended-gdbserver.exp as tool-and-target-specific interface file.
 Running src/gdb/testsuite/gdb.base/signest.exp ...
 ERROR: GDB process no longer exists

Debugging the core, we see infinite recursion:

 (top-gdb) bt 20
 #0  0x0000561d6a1bfeff in frame_unwind_arch (next_frame=0x561d6b19f9c0) at src/gdb/frame.c:2950
 #1  0x0000561d6a1bfeb8 in get_frame_arch (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:2939
 #2  0x0000561d6a1b989f in frame_unwind_find_by_frame (this_frame=0x561d6b19f9c0, this_cache=0x561d6b19f9d8) at src/gdb/frame-unwind.c:174
 #3  0x0000561d6a1bff04 in frame_unwind_arch (next_frame=0x561d6b19f9c0) at src/gdb/frame.c:2950
 #4  0x0000561d6a1bfeb8 in get_frame_arch (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:2939
 #5  0x0000561d6a1b989f in frame_unwind_find_by_frame (this_frame=0x561d6b19f9c0, this_cache=0x561d6b19f9d8) at src/gdb/frame-unwind.c:174
 #6  0x0000561d6a1bff04 in frame_unwind_arch (next_frame=0x561d6b19f9c0) at src/gdb/frame.c:2950
 #7  0x0000561d6a1bfeb8 in get_frame_arch (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:2939
 #8  0x0000561d6a1b989f in frame_unwind_find_by_frame (this_frame=0x561d6b19f9c0, this_cache=0x561d6b19f9d8) at src/gdb/frame-unwind.c:174
 #9  0x0000561d6a1bff04 in frame_unwind_arch (next_frame=0x561d6b19f9c0) at src/gdb/frame.c:2950
 #10 0x0000561d6a1bfeb8 in get_frame_arch (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:2939
 #11 0x0000561d6a1b989f in frame_unwind_find_by_frame (this_frame=0x561d6b19f9c0, this_cache=0x561d6b19f9d8) at src/gdb/frame-unwind.c:174
 #12 0x0000561d6a1bff04 in frame_unwind_arch (next_frame=0x561d6b19f9c0) at src/gdb/frame.c:2950
 #13 0x0000561d6a1bfeb8 in get_frame_arch (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:2939
 #14 0x0000561d6a1b989f in frame_unwind_find_by_frame (this_frame=0x561d6b19f9c0, this_cache=0x561d6b19f9d8) at src/gdb/frame-unwind.c:174
 #15 0x0000561d6a1bff04 in frame_unwind_arch (next_frame=0x561d6b19f9c0) at src/gdb/frame.c:2950
 #16 0x0000561d6a1bfeb8 in get_frame_arch (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:2939
 #17 0x0000561d6a1b989f in frame_unwind_find_by_frame (this_frame=0x561d6b19f9c0, this_cache=0x561d6b19f9d8) at src/gdb/frame-unwind.c:174
 #18 0x0000561d6a1bff04 in frame_unwind_arch (next_frame=0x561d6b19f9c0) at src/gdb/frame.c:2950
 #19 0x0000561d6a1bfeb8 in get_frame_arch (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:2939
 (More stack frames follow...)

 (top-gdb) bt -30
 #157054 0x0000561d6a1bfeb8 in get_frame_arch (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:2939
 #157055 0x0000561d6a1b989f in frame_unwind_find_by_frame (this_frame=0x561d6b19f9c0, this_cache=0x561d6b19f9d8) at src/gdb/frame-unwind.c:174
 #157056 0x0000561d6a1bff04 in frame_unwind_arch (next_frame=0x561d6b19f9c0) at src/gdb/frame.c:2950
 #157057 0x0000561d6a1bfeb8 in get_frame_arch (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:2939
 #157058 0x0000561d6a1b989f in frame_unwind_find_by_frame (this_frame=0x561d6b19f9c0, this_cache=0x561d6b19f9d8) at src/gdb/frame-unwind.c:174
 #157059 0x0000561d6a1bff04 in frame_unwind_arch (next_frame=0x561d6b19f9c0) at src/gdb/frame.c:2950
 #157060 0x0000561d6a1bbc65 in frame_unwind_pc (this_frame=0x561d6b19f9c0) at src/gdb/frame.c:970
 #157061 0x0000561d6a1bf54c in get_frame_pc (frame=0x561d6b19fa90) at src/gdb/frame.c:2625
 #157062 0x0000561d6a1bf63e in get_frame_address_in_block (this_frame=0x561d6b19fa90) at src/gdb/frame.c:2655
 #157063 0x0000561d6a0cae7f in dwarf2_frame_cache (this_frame=0x561d6b19fa90, this_cache=0x561d6b19faa8) at src/gdb/dwarf2/frame.c:1010
 #157064 0x0000561d6a0cb928 in dwarf2_frame_this_id (this_frame=0x561d6b19fa90, this_cache=0x561d6b19faa8, this_id=0x561d6b19faf0) at src/gdb/dwarf2/frame.c:1227
 #157065 0x0000561d6a1baf72 in compute_frame_id (fi=0x561d6b19fa90) at src/gdb/frame.c:588
 #157066 0x0000561d6a1bb16e in get_frame_id (fi=0x561d6b19fa90) at src/gdb/frame.c:636
 #157067 0x0000561d6a1bb224 in get_stack_frame_id (next_frame=0x561d6b19fa90) at src/gdb/frame.c:650
 #157068 0x0000561d6a26ecd0 in insert_hp_step_resume_breakpoint_at_frame (return_frame=0x561d6b19fa90) at src/gdb/infrun.c:7809
 #157069 0x0000561d6a26b88a in handle_signal_stop (ecs=0x7ffc67022830) at src/gdb/infrun.c:6428
 #157070 0x0000561d6a269d81 in handle_inferior_event (ecs=0x7ffc67022830) at src/gdb/infrun.c:5741
 #157071 0x0000561d6a265bd0 in fetch_inferior_event () at src/gdb/infrun.c:4120
 #157072 0x0000561d6a244c24 in inferior_event_handler (event_type=INF_REG_EVENT) at src/gdb/inf-loop.c:41
 #157073 0x0000561d6a435cc4 in remote_async_serial_handler (scb=0x561d6b4a8990, context=0x561d6b4a4c48) at src/gdb/remote.c:14403
 #157074 0x0000561d6a460bc5 in run_async_handler_and_reschedule (scb=0x561d6b4a8990) at src/gdb/ser-base.c:138
 #157075 0x0000561d6a460cae in fd_event (error=0, context=0x561d6b4a8990) at src/gdb/ser-base.c:189
 #157076 0x0000561d6a76a191 in handle_file_event (file_ptr=0x561d6b233ae0, ready_mask=1) at src/gdbsupport/event-loop.cc:575
 #157077 0x0000561d6a76a743 in gdb_wait_for_event (block=1) at src/gdbsupport/event-loop.cc:701
 #157078 0x0000561d6a7694ee in gdb_do_one_event () at src/gdbsupport/event-loop.cc:237
 #157079 0x0000561d6a2df16b in start_event_loop () at src/gdb/main.c:421
 #157080 0x0000561d6a2df2b6 in captured_command_loop () at src/gdb/main.c:481
 #157081 0x0000561d6a2e0d16 in captured_main (data=0x7ffc67022bd0) at src/gdb/main.c:1353
 #157082 0x0000561d6a2e0da8 in gdb_main (args=0x7ffc67022bd0) at src/gdb/main.c:1370
 #157083 0x0000561d69eb3d82 in main (argc=13, argv=0x7ffc67022cf8, envp=0x7ffc67022d68) at src/gdb/gdb.c:33

This was caused by exists_non_stop_target flushing the frame cache via
scoped_restore_current_thread/switch_to_thread, while we're in the
middle of unwinding.

Fix this by making exists_non_stop_target only switch the inferior,
like done in target_pass_ctrlc.

The annota1.exp change is necessary because we'd get a regression
otherwise:

  @@ -238,8 +238,6 @@ Continuing.

   \032\032breakpoints-invalid

  -\032\032frames-invalid
  -
   \032\032breakpoint 3

   Breakpoint 3,
  @@ -276,7 +274,7 @@ printf.c
   \032\032pre-prompt
   (gdb)
   \032\032prompt
  -PASS: gdb.base/annota1.exp: continue to printf
  +FAIL: gdb.base/annota1.exp: continue to printf

... because this patch avoids flushing the frame cache that lead to
that missing frames-invalid.  We still need to match frames-invalid
because against gdbserver + "maint set target non-stop on", some other
code path flushes the frame cache resulting in the annotation being
emitted anyway.

gdb/ChangeLog:
yyyy-mm-dd  Pedro Alves  <pedro@palves.net>

	* target.c (exists_non_stop_target): Use
	scoped_restore_current_inferior and set_current_inferior instead
	of scoped_restore_current_thread / switch_to_inferior_no_thread.

Change-Id: I8402483ee755e64e54d8b7c4a67c177557f569bd
This commit is contained in:
Pedro Alves
2021-06-03 19:39:19 +01:00
parent d9bda17252
commit de89924a63
2 changed files with 11 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
gdb/target.c
View File

@@ -4390,11 +4390,18 @@ exists_non_stop_target ()
if (target_is_non_stop_p ()) if (target_is_non_stop_p ())
return true; return true;
scoped_restore_current_thread restore_thread; /* We can get here quite deep in core code, e.g., from
target_terminal::inferior(). Avoid switching thread context or
anything that would communicate with the target (e.g., to fetch
registers), or flushing e.g., the frame cache, as we may end up
called from within the frame building code. We just switch
inferior in order to be able to call through the
target_stack. */
scoped_restore_current_inferior restore_inferior;
for (inferior *inf : all_inferiors ()) for (inferior *inf : all_inferiors ())
{ {
switch_to_inferior_no_thread (inf); set_current_inferior (inf);
if (target_is_non_stop_p ()) if (target_is_non_stop_p ())
return true; return true;
} }

3
gdb/testsuite/gdb.base/annota1.exp
View File

@@ -24,6 +24,7 @@ if ![target_can_use_run_cmd] {
} }
set breakpoints_invalid "\r\n\032\032breakpoints-invalid\r\n" set breakpoints_invalid "\r\n\032\032breakpoints-invalid\r\n"
set frames_invalid "\r\n\032\032frames-invalid\r\n"
# #
# test running programs # test running programs
@@ -226,7 +227,7 @@ gdb_test_multiple "break printf" "break printf" {
# #
# get to printf # get to printf
# #
set pat_begin "\r\n\032\032post-prompt\r\nContinuing.\r\n\r\n\032\032starting\r\n\r\n\032\032frames-invalid\r\n${breakpoints_invalid}\r\n\032\032frames-invalid\r\n" set pat_begin "\r\n\032\032post-prompt\r\nContinuing.\r\n\r\n\032\032starting\r\n${frames_invalid}${breakpoints_invalid}(${frames_invalid})?"
set pat_adjust "warning: Breakpoint 3 address previously adjusted from $hex to $hex.\r\n" set pat_adjust "warning: Breakpoint 3 address previously adjusted from $hex to $hex.\r\n"
set pat_end "\r\n\032\032breakpoint 3\r\n\r\nBreakpoint 3, \r\n\032\032frame-begin 0 $hex\r\n\r\n(\032\032frame-address\r\n$hex\r\n\032\032frame-address-end\r\n in \r\n)*.*\032\032frame-function-name\r\n.*printf(@.*)?\r\n\032\032frame-args\r\n.*\032\032frame-end\r\n\r\n\032\032stopped\r\n$gdb_prompt$" set pat_end "\r\n\032\032breakpoint 3\r\n\r\nBreakpoint 3, \r\n\032\032frame-begin 0 $hex\r\n\r\n(\032\032frame-address\r\n$hex\r\n\032\032frame-address-end\r\n in \r\n)*.*\032\032frame-function-name\r\n.*printf(@.*)?\r\n\032\032frame-args\r\n.*\032\032frame-end\r\n\r\n\032\032stopped\r\n$gdb_prompt$"