Re: 'set debug lin-lwp 1' seems broken with GDB/MI

On 2018-03-19 10:35, Dmitry Antipov wrote:
> On x86_64 GNU/Linux target, 'set debug lin-lwp 1' works as expected in
> CLI mode...
> 
> $ ~/.local/gdb-8.1.50/bin/gdb -q
> (gdb) set debug lin-lwp 1
> (gdb) attach 30460
> Attaching to process 30460
> sigchld
> LNA: waitpid 30460, saving status Stopped (signal) (stopped)
> PTRACE_ATTACH LWP 30461, 0, 0 (OK)
> [New LWP 30461]
> PTRACE_ATTACH LWP 30462, 0, 0 (OK)
> sigchld
> sigchld
> [New LWP 30462]
> LNSL: running -> suspending LWP 30462
> LNSL: running -> suspending LWP 30461
> LNSL: already stopped/no stop_requested yet LWP 30460
> linux_nat_wait: [process -1], [TARGET_WNOHANG]
> RSRL: NOT resuming LWP LWP 30462, not stopped
> RSRL: NOT resuming LWP LWP 30461, not stopped
> RSRL: NOT resuming LWP LWP 30460, has pending status
> LLW: enter
> LLW: Using pending wait status Stopped (signal) (stopped) for LWP 
> 30460.
> LLW: exit
> LNSL: running -> suspending LWP 30461
> linux-nat: already stopping LWP 30461 at GDB's request
> LNSL: running -> suspending LWP 30462
> linux-nat: already stopping LWP 30462 at GDB's request
> linux_nat_wait: [process -1], []
> RSRL: NOT resuming LWP LWP 30462, not stopped
> RSRL: NOT resuming LWP LWP 30461, not stopped
> RSRL: NOT resuming LWP LWP 30460, not resumed
> LLW: enter
> LNW: waitpid(-1, ...) returned 30462, ERRNO-OK
> LLW: waitpid 30462 received Stopped (signal) (stopped)
> LLW: resume_stop SIGSTOP caught for LWP 30462.
> LNW: waitpid(-1, ...) returned 30461, ERRNO-OK
> LLW: waitpid 30461 received Stopped (signal) (stopped)
> LLW: resume_stop SIGSTOP caught for LWP 30461.
> LNW: waitpid(-1, ...) returned 0, ERRNO-OK
> RSRL: NOT resuming LWP LWP 30462, has pending status
> RSRL: NOT resuming LWP LWP 30461, has pending status
> RSRL: NOT resuming LWP LWP 30460, not resumed
> SEL: Found 2 events, selecting #0
> LLW: exit
> sigchld
> sigchld
> sigchld
> RSRL: NOT resuming LWP LWP 30462, not resumed
> RSRL: NOT resuming LWP LWP 30461, has pending status
> RSRL: NOT resuming LWP LWP 30460, not resumed
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib64/libthread_db.so.1".
> linux_nat_wait: [process -1], []
> RSRL: NOT resuming LWP Thread 0x7fba253fa700 (LWP 30462), not resumed
> RSRL: NOT resuming LWP Thread 0x7fba25bfb700 (LWP 30461), has pending 
> status
> RSRL: NOT resuming LWP Thread 0x7fba26cb1740 (LWP 30460), not resumed
> LLW: enter
> LLW: Using pending wait status Stopped (signal) (stopped) for Thread
> 0x7fba25bfb700 (LWP 30461).
> LLW: exit
> 0x00007fba25fba8ad in pthread_join () from /lib64/libpthread.so.0
> 
> ...but not with MI:
> 
> $ ~/.local/gdb-8.1.50/bin/gdb -q -i=mi2
> =thread-group-added,id="i1"
> =cmd-param-changed,param="auto-load safe-path",value="/"
> (gdb)
> -gdb-set debug lin-lwp 1
> ^done
> (gdb)
> -target-attach 30460
> =thread-group-started,id="i1",pid="30460"
> ~"../../gdb/ui-file.h:59: internal-error: virtual void
> ui_file::write_async_safe(const char*, long int): write_async_safe\nA
> problem internal to GDB has been detected,\nfurther debugging may
> prove unreliable.\nQuit this debugging session? (y or n) "
> 
> Observed on 8.1 release as well.
> 
> Dmitry

Hi Dmitry,

I posted a patch here, could you take a look and test if it fixes the 
problem for you?

https://sourceware.org/ml/gdb-patches/2018-03/msg00488.html

Thanks,

Simon