[PATCH] Fix-for-multiple-thread-detection-in-AIX.patch

[Aditya Kamath1 <Aditya.Kamath1@ibm.com>]

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Hi,

Folks using AIX are not able to debug multiple threads.

The reason:- Since a new thread addition causes a thread target to wait, in AIX once the event ptid is got with the waitpid(), we need to set the inferior_ptid variable. Every time we come into aix_thread_target::wait() we check if libpthdebug might be ready to be initialized.In doing so we call pd_activate(). Here the session needs to be successfully initialised failing to which just a pid is returned. We do not enter pd_update() in the former case to take care of the rest of the thread addition process. The pthdb_session_init() is dependent on inferior_ptid variable as per our observations to return PTHDB_SUCCESS.

Please find attached the patch. [See: Fix-for-multiple-thread-detection-in-AIX.patch]

This can be shown by the following program:-


#include <stdio.h>

#include <unistd.h>

#include <stdlib.h>

#include <pthread.h>

#include <assert.h>


pthread_barrier_t barrier;


#define NUM_THREADS 2


void *

thread_function (void *arg)

{

  /* This ensures that the breakpoint is only hit after both threads

     are created, so the test can always switch to the non-event

     thread when the breakpoint triggers.  */

  pthread_barrier_wait (&barrier);


  while (1); /* break here */

}


int

main (void)

{

  int i;


  alarm (300);


  pthread_barrier_init (&barrier, NULL, NUM_THREADS);


  for (i = 0; i < NUM_THREADS; i++)

    {

      pthread_t thread;

      int res;


      res = pthread_create (&thread, NULL,

                            thread_function, NULL);

      assert (res == 0);

    }


  while (1)

    sleep (1);


  return 0;

}

Output without patch:-

(gdb) r

Starting program: /home/aditya/gdb_tests/continue-pending-status

^C

Program received signal SIGINT, Interrupt.

0xd0595fb0 in _p_nsleep () from /usr/lib/libpthread.a(shr_xpg5.o)

(gdb) info threads

  Id   Target Id         Frame

* 1    process 29557240  0xd0595fb0 in _p_nsleep () from /usr/lib/libpthread.a(shr_xpg5.o)

(gdb)



Output with patch:-


Reading symbols from /home/aditya/gdb_tests/continue-pending-status...

(gdb) r

Starting program: /home/aditya/gdb_tests/continue-pending-status

[New Thread 1]

^C[New Thread 258]

[New Thread 515]


Thread 1 received signal SIGINT, Interrupt.

0xd0595fb0 in _p_nsleep () from /usr/lib/libpthread.a(shr_xpg5.o)

(gdb) info threads

  Id   Target Id                           Frame

* 1    process 29557210                    0xd0595fb0 in _p_nsleep ()

   from /usr/lib/libpthread.a(shr_xpg5.o)

  2    Thread 1 (tid 120197499, running)   0xd0595fb0 in _p_nsleep ()

   from /usr/lib/libpthread.a(shr_xpg5.o)

  3    Thread 258 (tid 130486575, running) thread_function (arg=0x0)

    at continue-pending-status.c:36

  4    Thread 515 (tid 131666371, running) thread_function (arg=warning: (Internal error: pc 0x0 in read in psymtab, but not in symtab.)


0x0)

    at continue-pending-status.c:36

(gdb)

The gdb base test suite numbers with patch:-

# of expected passes            14094

# of unexpected failures        8770

# of unexpected successes       1

# of expected failures          10

# of known failures             46

# of unresolved testcases       121

# of untested testcases         84

# of unsupported tests          61

# of paths in test names        2

# of duplicate test names       5


Kindly let me know what you think.

Thanks and regards,
Aditya.



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From 7e8abe258f67abd3854fedf54e43da2b13541986 Mon Sep 17 00:00:00 2001
From: Aditya Vidyadhar Kamath <Aditya.Kamath1@ibm.com>
Date: Fri, 15 Jul 2022 08:40:25 -0500
Subject: [PATCH] Fix for multiple thread detection in AIX

---
 gdb/aix-thread.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/gdb/aix-thread.c b/gdb/aix-thread.c
index d47f5132592..f66b5904ae8 100644
--- a/gdb/aix-thread.c
+++ b/gdb/aix-thread.c
@@ -1088,6 +1088,10 @@ aix_thread_target::wait (ptid_t ptid, struct target_waitstatus *status,
      pid-only ptids.  */
   gdb_assert (ptid.is_pid ());
 
+  /* In pd_activate to get PTHB_SUCCESS in pthread debug session init
+     we need inferior_ptid set to update multiple threads. */
+  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)
-- 
2.31.1