[Bug gdb/30252] New: gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[Bug gdb/30252] New: gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[petr.sumbera at oracle dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

            Bug ID: 30252
           Summary: gdb-13.1/gdb/target.c:2641: internal-error:
                    target_resume: Assertion `inferior_ptid != null_ptid'
                    failed
           Product: gdb
           Version: 13.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: petr.sumbera at oracle dot com
  Target Milestone: ---

I see following regression/internal-error when using gdb (13.1) on Solaris x86:

(gdb) run -P
Starting program: /usr/bin/firefox -P
[Thread debugging using libthread_db enabled]
warning: could not convert 'mutex_t' from the host encoding (ISO-8859-1) to
UTF-32.
This normally should not happen, please file a bug report.
[New Thread 1 (LWP 1)]
/builds/psumbera/userland-gdb-13/components/gdb/gdb-13.1/gdb/target.c:2641:
internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
----- Backtrace -----
0x9b6213 ???
0xd3e52c ???
0xd3e778 ???
0xe798bc ???
0xcee510 ???
0xbdefca ???
0xc7273b ???
0xcf1443 ???
0xb3b9c4 ???
0xb4d008 ???
0x979b2f ???
0xe7a684 ???
0xb777f1 ???
0xb791e4 ???
0x922da6 ???
0x922c12 ???
---------------------
/builds/psumbera/userland-gdb-13/components/gdb/gdb-13.1/gdb/target.c:2641:
internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.

--

I used git bisect and it says:

d51926f06a7f4854bebdd71dcb0a78dbaa2f4168 is the first bad commit
commit d51926f06a7f4854bebdd71dcb0a78dbaa2f4168
Author: Pedro Alves <pedro@palves.net>
Date:   Thu Apr 21 14:20:36 2022 +0100

    Slightly tweak and clarify target_resume's interface

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[Bug gdb/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[petr.sumbera at oracle dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

Petr Šumbera <petr.sumbera at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pedro at palves dot net

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[Bug gdb/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[petr.sumbera at oracle dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

--- Comment #1 from Petr Šumbera <petr.sumbera at oracle dot com> ---
The problematic commit added following two assertions:

https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gdb/target.c;h=0cebecfafc379534180a6563d246cdbc3488311e;hb=HEAD#l2648

2648   gdb_assert (inferior_ptid != null_ptid);
2649   gdb_assert (inferior_ptid.matches (scope_ptid));

When they are removed it seems to work as expected/before.

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org
          Component|gdb                         |tdep

--- Comment #2 from Tom Tromey <tromey at sourceware dot org> ---
I'm not super conversant with this area but I think that, most likely,
patching out these asserts will let it work in some scenarios but
crash in others.  Probably the native target needs some extra work here,
though unfortunately I don't know exactly what.

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[simark at simark dot ca]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

Simon Marchi <simark at simark dot ca> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |simark at simark dot ca

--- Comment #3 from Simon Marchi <simark at simark dot ca> ---
(In reply to Tom Tromey from comment #2)
> I'm not super conversant with this area but I think that, most likely,
> patching out these asserts will let it work in some scenarios but
> crash in others.  Probably the native target needs some extra work here,
> though unfortunately I don't know exactly what.

I agree.

Can you run the same test case, but with doing "set debug infrun 1" first?

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[petr.sumbera at oracle dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

--- Comment #4 from Petr Šumbera <petr.sumbera at oracle dot com> ---
Created attachment 14771
  --> https://sourceware.org/bugzilla/attachment.cgi?id=14771&action=edit
assertion hit with set debug infrun 1

Thanks for looking at it. What we are looking for?

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

--- Comment #5 from Pedro Alves <pedro at palves dot net> ---
The problem is that the backend called target_resume without switching to the
leader thread of that resumption.

- inferior_ptid is a global in gdb that points at the currently selected
thread.
- inferior_ptid == null_ptid means no thread is selected at that point.

- The target_resume interface is:

 /* Resume execution (or prepare for execution) of the current thread
    (INFERIOR_PTID), while optionally letting other threads of the
    current process or all processes run free.
    ...

Thus calling target_resume with inferior_ptid == null_ptid is bogus.

target_wait (which leads to procfs_target::wait on Solaris) is called with
inferior_ptid == null_ptid on entry exactly to help catch such bogus uses. 
It's procfs_target::wait that is calling target_resume incorrectly.  From the
backtrace, it seems that the line in question is 2187, which has:

                    /* How to keep going without returning to wfi: */
                    target_continue_no_signal (ptid);
                    goto wait_again;

target_continue_no_signal is a small wrapper around target_resume, which would
make sense.  I guess we don't see target_continue_no_signal in the backtrace
because that is an optimized gdb build.

I'm writing a fix.

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

--- Comment #6 from Pedro Alves <pedro at palves dot net> ---
Created attachment 14777
  --> https://sourceware.org/bugzilla/attachment.cgi?id=14777&action=edit
Fix

Could you give the attached patch a try?

I was able to confirm that gdb/procfs.c (the modified file) at least compiles
using an old Solaris 11 VM I had lying around, but I wasn't able to build GDB
fully due to other issues.

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[petr.sumbera at oracle dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

--- Comment #7 from Petr Šumbera <petr.sumbera at oracle dot com> ---
(In reply to Pedro Alves from comment #6)
> Created attachment 14777 [details]
> Fix
> 
> Could you give the attached patch a try?

Yes. Thank you! Assertion is not hit in my test case.

> I was able to confirm that gdb/procfs.c (the modified file) at least
> compiles using an old Solaris 11 VM I had lying around, but I wasn't able to
> build GDB fully due to other issues.

There is one year old release which you should be able to use for such testing:

https://blogs.oracle.com/solaris/post/building-open-source-software-on-oracle-solaris-114-cbe-release

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[marcel at telka dot sk]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

Marcel Telka <marcel at telka dot sk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marcel at telka dot sk

--- Comment #8 from Marcel Telka <marcel at telka dot sk> ---
I hit the same bug with gdb 13.2 on OpenIndiana (illumos based distro) and the
attached patch solved the problem.

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

--- Comment #9 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pedro Alves <palves@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b2ad7bb9e6a012699195d3eda9d40679c406ebdc

commit b2ad7bb9e6a012699195d3eda9d40679c406ebdc
Author: Pedro Alves <pedro@palves.net>
Date:   Thu Jul 6 15:05:11 2023 +0100

    Fix Solaris regression (PR tdep/30252)

    PR tdep/30252 reports that using GDB on Solaris fails an assertion in
    target_resume:

     target.c:2648: internal-error: target_resume: Assertion `inferior_ptid !=
null_ptid' failed.
     A problem internal to GDB has been detected,
     further debugging may prove unreliable.
     Quit this debugging session? (y or n)

    The backtrace, after running it through c++filt, looks like:

     ----- Backtrace -----
     0xa18914 gdb_internal_backtrace_1
             /root/binutils-gdb/gdb/bt-utils.c:122
     0xa18914 gdb_internal_backtrace()
             /root/binutils-gdb/gdb/bt-utils.c:168
     0xdec834 internal_vproblem
             /root/binutils-gdb/gdb/utils.c:401
     0xdecad8 internal_verror(char const*, int, char const*, __va_list_tag*)
             /root/binutils-gdb/gdb/utils.c:481
     0xf3638c internal_error_loc(char const*, int, char const*, ...)
             /root/binutils-gdb/gdbsupport/errors.cc:58
     0xd70580 target_resume(ptid_t, int, gdb_signal)
             /root/binutils-gdb/gdb/target.c:2648
     0xc59e85 procfs_target::wait(ptid_t, target_waitstatus*,
enum_flags<target_wait_flag>)
             /root/binutils-gdb/gdb/procfs.c:2187
     0xcf6da7 sol_thread_target::wait(ptid_t, target_waitstatus*,
enum_flags<target_wait_flag>)
             /root/binutils-gdb/gdb/sol-thread.c:442
     0xd73711 target_wait(ptid_t, target_waitstatus*,
enum_flags<target_wait_flag>)
             /root/binutils-gdb/gdb/target.c:2586
     ...

    The problem is that the procfs backend, while inside target_wait,
    called target_resume without switching to the leader thread of that
    resumption.

    The target_resume interface is:

     /* Resume execution (or prepare for execution) of the current thread
        (INFERIOR_PTID), while optionally letting other threads of the
        current process or all processes run free.
        ...

    Thus calling target_resume with inferior_ptid == null_ptid is bogus.

    target_wait (which leads to procfs_target::wait on Solaris) is called
    with inferior_ptid == null_ptid on entry exactly to help catch such
    bogus uses.

    From the backtrace, it seems that the relevant line in question is
    procfs.c:2187:

    2186  /* How to keep going without returning to wfi: */
    2187  target_continue_no_signal (ptid);
    2188  goto wait_again;

    target_continue_no_signal is a small wrapper around target_resume,
    which would make sense.

    The fix is to not call target_resume or go via the target stack at
    all.  Instead, factor out a new proc_resume function out of
    procfs_target::resume, and call that.  The new function does not rely
    on inferior_ptid.

    I've not been able to test it myself, but Petr confirmed it fixes the
    assertion failure with his test case, and Marcel Telka also confirmed
    it solves the problem.

    Tested-By: Petr Å umbera <petr.sumbera@oracle.com>
    Tested-By: Marcel Telka <marcel@telka.sk>
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30252
    Change-Id: I6213c59b081d400a22e799ee621c2eff6dcafbf3

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

--- Comment #10 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The gdb-13-branch branch has been updated by Pedro Alves
<palves@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=dfe07f10de81a38f595022556873d16585ea2b7e

commit dfe07f10de81a38f595022556873d16585ea2b7e
Author: Pedro Alves <pedro@palves.net>
Date:   Thu Jul 6 15:05:11 2023 +0100

    Fix Solaris regression (PR tdep/30252)

    PR tdep/30252 reports that using GDB on Solaris fails an assertion in
    target_resume:

     target.c:2648: internal-error: target_resume: Assertion `inferior_ptid !=
null_ptid' failed.
     A problem internal to GDB has been detected,
     further debugging may prove unreliable.
     Quit this debugging session? (y or n)

    The backtrace, after running it through c++filt, looks like:

     ----- Backtrace -----
     0xa18914 gdb_internal_backtrace_1
             /root/binutils-gdb/gdb/bt-utils.c:122
     0xa18914 gdb_internal_backtrace()
             /root/binutils-gdb/gdb/bt-utils.c:168
     0xdec834 internal_vproblem
             /root/binutils-gdb/gdb/utils.c:401
     0xdecad8 internal_verror(char const*, int, char const*, __va_list_tag*)
             /root/binutils-gdb/gdb/utils.c:481
     0xf3638c internal_error_loc(char const*, int, char const*, ...)
             /root/binutils-gdb/gdbsupport/errors.cc:58
     0xd70580 target_resume(ptid_t, int, gdb_signal)
             /root/binutils-gdb/gdb/target.c:2648
     0xc59e85 procfs_target::wait(ptid_t, target_waitstatus*,
enum_flags<target_wait_flag>)
             /root/binutils-gdb/gdb/procfs.c:2187
     0xcf6da7 sol_thread_target::wait(ptid_t, target_waitstatus*,
enum_flags<target_wait_flag>)
             /root/binutils-gdb/gdb/sol-thread.c:442
     0xd73711 target_wait(ptid_t, target_waitstatus*,
enum_flags<target_wait_flag>)
             /root/binutils-gdb/gdb/target.c:2586
     ...

    The problem is that the procfs backend, while inside target_wait,
    called target_resume without switching to the leader thread of that
    resumption.

    The target_resume interface is:

     /* Resume execution (or prepare for execution) of the current thread
        (INFERIOR_PTID), while optionally letting other threads of the
        current process or all processes run free.
        ...

    Thus calling target_resume with inferior_ptid == null_ptid is bogus.

    target_wait (which leads to procfs_target::wait on Solaris) is called
    with inferior_ptid == null_ptid on entry exactly to help catch such
    bogus uses.

    From the backtrace, it seems that the relevant line in question is
    procfs.c:2187:

    2186  /* How to keep going without returning to wfi: */
    2187  target_continue_no_signal (ptid);
    2188  goto wait_again;

    target_continue_no_signal is a small wrapper around target_resume,
    which would make sense.

    The fix is to not call target_resume or go via the target stack at
    all.  Instead, factor out a new proc_resume function out of
    procfs_target::resume, and call that.  The new function does not rely
    on inferior_ptid.

    I've not been able to test it myself, but Petr confirmed it fixes the
    assertion failure with his test case, and Marcel Telka also confirmed
    it solves the problem.

    Tested-By: Petr Å umbera <petr.sumbera@oracle.com>
    Tested-By: Marcel Telka <marcel@telka.sk>
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30252
    Change-Id: I6213c59b081d400a22e799ee621c2eff6dcafbf3

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[Bug tdep/30252] gdb-13.1/gdb/target.c:2641: internal-error: target_resume: Assertion `inferior_ptid != null_ptid' failed

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=30252

Pedro Alves <pedro at palves dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.1
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #11 from Pedro Alves <pedro at palves dot net> ---
Thanks for extra confirmation Marcel, I would have forgotten about this patch
without it.

I've now merged the patch to both master and the gdb 13 branch.  I am not sure
if there will ever be another GDB 13 release, most likely there won't, but, if
you need to pull the fix for some downstream release, it's there.

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