RE: [PATCH] Use current_inferior ()->pid for AIX

[Aditya Vidyadhar Kamath <ADITYA.VIDYADHAR.KAMATH@ibm.com>]

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Hi all,

While testing programs in AIX I noticed that GDB crashes when an
inferior exits, with this error:

  inferior.c:293: internal- error: inferior* find_inferior_pid(process_stratum_target*, int): Assertion `pid != 0' failed.

When a process exits inferior_ptid.pid is set to 0. Unfortunately, the rs6000-aix-nat target is still relying on the value of
inferior_ptid in the case where an inferior exits - we return the
value of inferior_ptid as the pid of the process that exited.

The waitpid() system call suspends execution of the calling process until a child specified by pid argument has changed state. Once the inferior [assuming there is only one inferior] dies, waitpid() has no child to return.

Due to this an ERRCHLD error is returned thereby returning an inferior_ptid.pid with 0 leading to this assertion failure.

This patch is a fix to the same where we use the pid returned by the beneath wait using waitpid and adjust our inferior_ptid so that the rest of the code will take in the right values of both inferior_ptid and current_inferior.

The following are the test results after running gdb.base test suite with the patch.
# of expected passes 26244
# of unexpected failures 4230
# of unexpected successes 1
# of expected failures 17
# of known failures 26
# of unresolved testcases 110
# of untested testcases 79
# of unsupported tests 62
# of paths in test names 1
# of duplicate test names 4

The following are test results after running gdb.base test suite without the patch.
# of expected passes 12935
# of unexpected failures 1988
# of unexpected successes 1
# of expected failures 3
# of known failures 6
# of unresolved testcases 159
# of untested testcases 77
# of unsupported tests 39
# of paths in test names 2
# of duplicate test names 13

Please find attached the patch. [See 0001-Fix-gdb_assert-pid-0-assertion-failure-in-AIX.patch].

Have a nice day ahead,

Thanks and regards,
Aditya.


________________________________
From: Simon Marchi <simon.marchi@polymtl.ca>
Sent: Monday, May 30, 2022 6:15 PM
To: Aditya Vidyadhar Kamath <ADITYA.VIDYADHAR.KAMATH@ibm.com>
Cc: Sangamesh Mallayya <sangamesh.swamy@in.ibm.com>; Simon Marchi via Gdb-patches <gdb-patches@sourceware.org>
Subject: [EXTERNAL] Re: [PATCH] Use current_inferior ()->pid for AIX

Hi,

Re-adding gdb-patches, since it's information useful to everybody.

On 2022-05-29 23:41, Aditya Vidyadhar Kamath wrote:
> Hi Simon,
>
> Thank you so much for the feedback. Yes it makes sense. As I was trying to fix this we need one more information that will help us.
>
> Once an inferior finishes its execution where is the inferior_ptid's pid variable set to 0. Or who is the one [file name or function name] that updates inferior_ptid class variable pid to 0.

This is done in the mourn_inferior target method.  Many targets call the
generic_mourn_inferior function, which calls switch_to_no_thread, which
sets current_thread_ to nullptr and inferior_ptid to null_ptid.

Simon

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From f8259070349b075f65a4b9fe0a888543a6864f6e Mon Sep 17 00:00:00 2001
From: "aditya@ibm" <aditya.vidyadhar.kamath@ibm.com>
Date: Fri, 10 Jun 2022 08:50:46 -0500
Subject: [PATCH] Fix gdb_assert (pid != 0); assertion failure in AIX

---
 gdb/aix-thread.c     | 5 +++++
 gdb/rs6000-aix-nat.c | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/gdb/aix-thread.c b/gdb/aix-thread.c
index ecd8200b692..3037d73c5c4 100644
--- a/gdb/aix-thread.c
+++ b/gdb/aix-thread.c
@@ -1079,6 +1079,7 @@ ptid_t
 aix_thread_target::wait (ptid_t ptid, struct target_waitstatus *status,
 			 target_wait_flags options)
 {
+  struct inferior *inf;
   {
     scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
 
@@ -1091,6 +1092,10 @@ aix_thread_target::wait (ptid_t ptid, struct target_waitstatus *status,
   if (ptid.pid () == -1)
     return ptid_t (-1);
 
+  inf = find_inferior_pid(current_inferior ()->process_target (),ptid.pid());
+  if(inf != NULL){
+   inferior_ptid = ptid;
+  }
   /* Check whether libpthdebug might be ready to be initialized.  */
   if (!pd_active && status->kind () == TARGET_WAITKIND_STOPPED
       && status->sig () == GDB_SIGNAL_TRAP)
diff --git a/gdb/rs6000-aix-nat.c b/gdb/rs6000-aix-nat.c
index 8563aea313a..8a0c074be8f 100644
--- a/gdb/rs6000-aix-nat.c
+++ b/gdb/rs6000-aix-nat.c
@@ -529,7 +529,7 @@ rs6000_nat_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus,
 	}
 
       /* Ignore terminated detached child processes.  */
-      if (!WIFSTOPPED (status) && pid != inferior_ptid.pid ())
+      if (!WIFSTOPPED (status) && pid != inferior_ptid.pid () && inferior_ptid.pid () != 0)
 	pid = -1;
     }
   while (pid == -1);
-- 
2.31.1