[Bug symtab/16405] New: call-sites lock up backtrace on Fedora 20

[Bug symtab/16405] New: call-sites lock up backtrace on Fedora 20

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

            Bug ID: 16405
           Summary: call-sites lock up backtrace on Fedora 20
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: symtab
          Assignee: unassigned at sourceware dot org
          Reporter: jan.kratochvil at redhat dot com
            Target: x86_64-unknown-linux-gnu

Attempt to backtrace LibreOffice on Fedora 20 x86_64 locks up, each frame gets
up to minutes to print, GDB RSS grows to 1GB and more.

The queue in process_queue() in the backtrace below (randomly stopped GDB) had
166 symtab entries.

It is probably a regression since call sites exist; unaware why it did not
reproduce before.  But expansion of a single symtab should not cause 166
symtabs to be expanded.

FAIL: GNU gdb (GDB) 7.6.50.20140107-cvs
FAIL: GNU gdb (GDB) 7.6.1.20131021-cvs
FAIL: gdb-7.6.50.20130731-16.fc20.x86_64
N/A:  GNU gdb (GDB) 7.5.1.20130125-cvs - it cannot parse Fedora 20 DWARF


LibreOffice backtrace:
(gdb) bt
Python Exception <type 'exceptions.ImportError'> No module named gdb.frames: 
#0  0x0000003eaaceaa8d in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x0000003ead4495b4 in g_main_context_poll (priority=2147483647, n_fds=3,
fds=0x14da140, timeout=9915, 
    context=0xa4db60) at gmain.c:4007
#2  g_main_context_iterate (context=context@entry=0xa4db60,
block=block@entry=1, dispatch=dispatch@entry=1, 
    self=<optimized out>) at gmain.c:3708
<locked up>


GDB backtrace:
#0  process_queue
#1  in dw2_do_instantiate_symtab
#2  in dw2_instantiate_symtab
#3  in dw2_find_pc_sect_symtab
#4  in find_pc_sect_symtab
#5  in find_pc_symtab
#6  in call_site_for_pc
#7  in call_site_find_chain_1
#8  in call_site_find_chain
#9  in dwarf2_tailcall_sniffer_first
#10 in dwarf2_frame_prev_register
#11 in frame_unwind_register_value
#12 in frame_register_unwind
#13 in frame_register_unwind_location
#14 in get_prev_frame_1
#15 in get_prev_frame
#16 in value_of_dwarf_reg_entry
#17 in value_of_dwarf_block_entry
#18 in loclist_read_variable_at_entry
#19 in read_frame_arg
#20 in print_frame_args
#21 in print_frame
#22 in print_frame_info
#23 in backtrace_command_1
#24 in backtrace_command
#25 in do_cfunc
#26 in cmd_func
#27 in execute_command
#28 in command_handler
#29 in command_line_handler
#30 in rl_callback_read_char
#31 in rl_callback_read_char_wrapper
#32 in stdin_event_handler
#33 in handle_file_event
#34 in process_event
#35 in gdb_do_one_event
#36 in start_event_loop
#37 in cli_command_loop
#38 in current_interp_command_loop
#39 in captured_command_loop
#40 in catch_errors
#41 in captured_main
#42 in catch_errors
#43 in gdb_main
#44 in main

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[Bug symtab/16405] backtrace locks up on Fedora 20

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jan.kratochvil at redhat dot com
            Summary|call-sites lock up          |backtrace locks up on
                   |backtrace on Fedora 20      |Fedora 20

--- Comment #1 from Jan Kratochvil <jan.kratochvil at redhat dot com> ---
call-sites are really innocent, it is DWARF expansion problem in general.

I have patched out call-sites in GDB code and the problem remains.


#0  in start_subfile
#1  in dwarf2_start_subfile
#2  in dwarf_decode_lines 
#3  in handle_DW_AT_stmt_list
#4  in read_file_scope
#5  in process_die
#6  in process_full_comp_unit
#7  in process_queue
#8  in dw2_do_instantiate_symtab
#9  in dw2_instantiate_symtab
#10 in dw2_find_pc_sect_symtab
#11 in find_pc_sect_symtab
#12 in blockvector_for_pc_sect
#13 in block_for_pc_sect
#14 in block_for_pc
#15 in inline_frame_sniffer
#16 in frame_unwind_find_by_frame
#17 in compute_frame_id
#18 in get_prev_frame_if_no_cycle
#19 in get_prev_frame_1
#20 in get_prev_frame
#21 in value_of_dwarf_reg_entry
#22 in value_of_dwarf_block_entry
#23 in loclist_read_variable_at_entry
#24 in read_frame_arg
#25 in print_frame_args
#26 in print_frame
#27 in print_frame_info
#28 in backtrace_command_1
#29 in backtrace_command

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[Bug symtab/16405] backtrace locks up on Fedora 20

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at sourceware dot org   |jan.kratochvil at redhat dot com

--- Comment #2 from Jan Kratochvil <jan.kratochvil at redhat dot com> ---
Created attachment 7347
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7347&action=edit
draft patch

This patch:
bt
Command execution time: 0.472000 (cpu), 0.539249 (wall)
Space used: 380514304 (+44015616 for this command)
#symtabs: 30964 (+2457), #primary symtabs: 18 (+7), #blocks: 7877 (+7852)
+
thread apply all bt
Command execution time: 0.496000 (cpu), 0.500745 (wall)
Space used: 408891392 (+28377088 for this command)
#symtabs: 32294 (+1330), #primary symtabs: 31 (+13), #blocks: 16467 (+8590)

FSF GDB HEAD:
bt
Command execution time: 153.667000 (cpu), 154.234038 (wall)
Space used: 1283444736 (+946941952 for this command)
#symtabs: 4373195 (+4344688), #primary symtabs: 2376 (+2365), #blocks: 12593
(+12568)
+
thread apply all bt
Command execution time: 104.489000 (cpu), 104.961148 (wall)
Space used: 1768660992 (+485216256 for this command)
#symtabs: 6662638 (+2289443), #primary symtabs: 3673 (+1297), #blocks: 23751
(+11158)

But
  thread apply all bt full
is still slow.  One may omit DW_TAG_imported_unit even in this case thanks to
.gdb_index (if it points to the right CU, maybe it is not).  This still affects
for example ABRT.

gdb -p `pidof soffice.bin` -ex 'set pagination off' -ex 'maintenance set
per-command space' -ex 'maintenance set per-command symtab' -ex 'maintenance
set per-command time'

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[Bug symtab/16405] backtrace takes GBs and minutes with dwz -m

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|backtrace locks up on       |backtrace takes GBs and
                   |Fedora 20                   |minutes with dwz -m

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[Bug symtab/16405] backtrace takes GBs and minutes with dwz -m

[mjw at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

Mark Wielaard <mjw at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mjw at redhat dot com

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[Bug symtab/16405] backtrace takes GBs and minutes with dwz -m

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Attachment #7347|0                           |1
        is obsolete|                            |

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[Bug symtab/16405] backtrace takes GBs and minutes with dwz -m

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

--- Comment #3 from Jan Kratochvil <jan.kratochvil at redhat dot com> ---
[patch] Fix 100x slowdown regression on DWZ files
https://sourceware.org/ml/gdb-patches/2014-10/msg00020.html

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[Bug symtab/16405] backtrace takes GBs and minutes with dwz -m

[sergiodj at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

Sergio Durigan Junior <sergiodj at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sergiodj at redhat dot com

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[Bug symtab/16405] backtrace takes GBs and minutes with dwz -m

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Jan Kratochvil <jan.kratochvil at redhat dot com> ---
527f3840e1af8bc2e3173922ddae15d0021ed9b1 master
0325b9bae8037aaa69cdfc8aa43a46678474f261 7.9

time gdb -batch -q -p `pidof soffice.bin` -ex 'thread apply all bt full'|wc -l
174
real    0m6.805s

time gdb -batch -q -p `pidof soffice.bin` -ex 'thread apply all bt'|wc -l
61
real    0m3.635s

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[Bug symtab/16405] backtrace takes GBs and minutes with dwz -m

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16405

--- Comment #5 from Jan Kratochvil <jan.kratochvil at redhat dot com> ---
The Comment 4 benchmark is BTW bogus as it did not have expanded CUs.

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