[Bug tui/21817] New: gdb session suspended when run in background

["jim at realintent dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=21817

            Bug ID: 21817
           Summary: gdb session suspended when run in background
           Product: gdb
           Version: 7.12.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tui
          Assignee: unassigned at sourceware dot org
          Reporter: jim at realintent dot com
  Target Milestone: ---

Help!
I'm running gdb 7.12.1 under CentOS 6.8.

My application has a signal handler that invokes gdb in batch when a SEGV or 
other bad signals occur.  It invokes gdb with the application's process ID as
    gdb --pid=<pid> --nx -x cmd.gdb --batch
This had worked fine under RH-5 and older versions of gdb.
With gdb 7.12.1, the gdb process is immediately suspended before any commands
are run.

I debugged the suspended gdb process, which shows that gdb was stopped in 
set_tty_state().  This ought not to have happened, as gdb was run as a 
background process and should not have tried to configure the terminal.
The output of 'where' and 'backtrace full' are below.

Is there a workaround for this problem?

(gdb) where
#0  0x0000003a78ee0048 in tcsetattr () from /lib64/libc.so.6
#1  0x00000000004491e1 in set_tty_state (scb=<optimized out>, state=<optimized
out>) at ser-unix.c:152
#2  hardwire_set_tty_state (scb=<optimized out>, ttystate=<optimized out>) at
ser-unix.c:209
#3  0x0000000000660d4b in child_terminal_inferior (self=<optimized out>) at
inflow.c:276
#4  0x000000000044e5b9 in linux_nat_terminal_inferior (self=<optimized out>) at
linux-nat.c:4462
#5  0x0000000000587f09 in target_terminal_inferior () at target.c:501
#6  0x000000000053a8aa in attach_command (args=0x26bbf70 "11882",
args@entry=0x7ffce9adc284 "11882", from_tty=from_tty@entry=0) at infcmd.c:2863
#7  0x00000000005575b8 in catch_command_errors (command=0x53a810
<attach_command(char*, int)>, arg=arg@entry=0x7ffce9adc284 "11882", from_tty=0)
at main.c:375
#8  0x000000000055818b in captured_main (data=0x7ffce9ad9db0) at main.c:1065
#9  gdb_main (args=args@entry=0x7ffce9ad9ed0) at main.c:1159
#10 0x0000000000409595 in main (argc=<optimized out>, argv=<optimized out>) at
gdb.c:32

(gdb) backtrace full 
#0  0x0000003a78ee0048 in tcsetattr () from /lib64/libc.so.6
No symbol table info available.
#1  0x00000000004491e1 in set_tty_state (scb=<optimized out>, state=<optimized
out>) at ser-unix.c:152
No locals.
#2  hardwire_set_tty_state (scb=<optimized out>, ttystate=<optimized out>) at
ser-unix.c:209
        state = <optimized out>
#3  0x0000000000660d4b in child_terminal_inferior (self=<optimized out>) at
inflow.c:276
        result = <optimized out>
        inf = 0x27b2f20
        tinfo = 0x27b7cd0
#4  0x000000000044e5b9 in linux_nat_terminal_inferior (self=<optimized out>) at
linux-nat.c:4462
No locals.
#5  0x0000000000587f09 in target_terminal_inferior () at target.c:501
        ui = <optimized out>
#6  0x000000000053a8aa in attach_command (args=0x26bbf70 "11882",
args@entry=0x7ffce9adc284 "11882", from_tty=from_tty@entry=0) at infcmd.c:2863
        async_exec = 0
        attach_target = 0x0
        inferior = 0x27b2f20
        args_chain = 0x7a87e0 <sentinel_cleanup>
        mode = <optimized out>
#7  0x00000000005575b8 in catch_command_errors (command=0x53a810
<attach_command(char*, int)>, arg=arg@entry=0x7ffce9adc284 "11882", from_tty=0)
at main.c:375
        was_sync = 0
        exception_try_scope_instance = {saved_state = 0x26bc070}
#8  0x000000000055818b in captured_main (data=0x7ffce9ad9db0) at main.c:1065
        execarg = <optimized out>
        cdarg = 0x0
        save_auto_load = 1
        argc = <optimized out>
        ttyarg = 0x0
        cmdarg_vec = 0x26bc790
        system_gdbinit = 0x0
        inhibit_home_gdbinit = 0
        print_help = 0
        context = 0x7ffce9ad9db0
        argv = <optimized out>
        local_gdbinit = 0x0
        i = <optimized out>
        objfile = <optimized out>
        pre_stat_chain = 0x7a87e0 <sentinel_cleanup>
        pid_or_core_arg = 0x0
        cmdarg_p = 0x0
        home_gdbinit = 0x27b7d10 "/home/jim/.gdbinit"
        print_version = 0
        corearg = 0x0
        set_args = 0
        symarg = <optimized out>
        pidarg = 0x7ffce9adc284 "11882"
        dirarg = 0x26bbf70
        dirsize = 1
        ndir = <optimized out>
        quiet = 1
        print_configuration = 0
#9  gdb_main (args=args@entry=0x7ffce9ad9ed0) at main.c:1159
        exception_try_scope_instance = {saved_state = 0x7a87e0
<sentinel_cleanup>}
#10 0x0000000000409595 in main (argc=<optimized out>, argv=<optimized out>) at
gdb.c:32
        args = {argc = 6, argv = 0x7ffce9ad9fd8, interpreter_p = 0x755884
"console"}

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