From: Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
To: "simark@simark.ca" <simark@simark.ca>,
Aditya Kamath1 <Aditya.Kamath1@ibm.com>,
"gdb-patches@sourceware.org" <gdb-patches@sourceware.org>
Cc: Sangamesh Mallayya <sangamesh.swamy@in.ibm.com>
Subject: Re: [PATCH] 0001-Fix-multi-thread-debug-bug-in-AIX.patch
Date: Tue, 15 Nov 2022 18:16:01 +0000 [thread overview]
Message-ID: <f4add1d5301e06e7545c6f3a28f9e2b3457016f1.camel@de.ibm.com> (raw)
In-Reply-To: <CH2PR15MB3544E198B0622C3AD22597A2D6029@CH2PR15MB3544.namprd15.prod.outlook.com>
Aditya Kamath1 <Aditya.Kamath1@ibm.com> wrote:
>>So I think instead of adding a "priv" struct to that GDB thread
>>identifying the main process, the sync_threadlists routine should
>>actually just delete it (or replace it with the actual first thread,
>>whatever is easier).
>
>I have chosen not to add the first main thread as new thread. Instead,
>we carry on with main process thread itself adding private data to it.
>Kindly see the first if condition. I observed this with the linux folks
>where in their output as you mentioned do not add any new threads the
>first time on recognition of multi thread debugee for the main process.
OK, but this is still weird:
>* 1 process 26149278 0xd0595fb0 in _p_nsleep ()
> 2 Thread 258 (tid 24445361, running) thread_function (arg=0x0)
> 3 Thread 515 (tid 16187681, running) thread_function (arg=warning: (Internal error: pc 0x0 in read in psymtab, but not in symtab.)
Why does the first thread look so different? That's not the
case with Linux threads. I believe even if you re-use the
thread structure, you'll still need to switch the ptid to one
that indicates a thread instead of a non-threaded process.
>A couple of things I want to inform you is that the way the second
>for loop is executing is not correct from here on to sync both the
>buffer lists [pthread and GDB thread]. Since we are now not adding
>multiple threads for the same process main thread one representing
>the GDB thread and the other by the pthread those conditions and
>indices like pi and gi will fail. Now there has not pcount - 1
>threads in the GDB thread buffer always. Condition 2 and 3 in the
>patch take care of them for addition and deletion of threads.
The new logic doesn't look correct to me - note that it never
even looks at thread IDs any more, just the raw number of threads.
So for example if *any* thread exits, the code will always delete
the *last* thread from the GDB list - whether this is actually
the one that exited or not.
I do think it is necessary to compare thread IDs - you need to
map the thread IDs retrieved by libpthdebug against the thread
IDs already present in GDB's thread list. If a matching thread
ID is present in both lists, it should not be touched. If a
thread ID occurs only in the libpthdebug list, it needs to be
added to GDB's list. If a thread ID occurs only in GDB's list,
it needs to be removed from there.
That's what the old code attempted to do as far as I can see;
if it got it wrong in certain corner cases, they need to be fixed;
but completely removing that logic seems just wrong.
Bye,
Ulrich
next prev parent reply other threads:[~2022-11-15 18:16 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-25 6:47 Aditya Kamath1
2022-10-28 9:49 ` Ulrich Weigand
2022-11-08 12:00 ` Aditya Kamath1
2022-11-08 12:17 ` Ulrich Weigand
2022-11-13 18:15 ` Aditya Kamath1
2022-11-15 18:16 ` Ulrich Weigand [this message]
2022-11-21 8:27 ` Aditya Kamath1
2022-11-23 14:15 ` Ulrich Weigand
2022-11-23 16:03 ` Aditya Kamath1
2022-11-23 17:09 ` Ulrich Weigand
2022-11-23 18:45 ` Aditya Kamath1
2022-11-29 8:18 ` Aditya Kamath1
2022-11-30 14:57 ` Ulrich Weigand
2022-12-02 7:50 ` Aditya Kamath1
2022-12-05 18:33 ` Ulrich Weigand
2022-12-08 10:28 ` Aditya Kamath1
2022-12-08 10:46 ` Aditya Kamath1
2022-12-08 16:29 ` Ulrich Weigand
2022-12-15 12:58 ` Aditya Kamath1
2022-12-15 15:53 ` Ulrich Weigand
2022-12-19 6:30 ` Aditya Kamath1
2022-12-22 12:50 ` Ulrich Weigand
2022-12-26 13:18 ` Aditya Kamath1
2023-01-09 14:04 ` Ulrich Weigand
2023-01-10 12:23 ` Aditya Kamath1
2023-01-11 13:31 ` Ulrich Weigand
2023-01-13 14:06 ` Aditya Kamath1
2023-01-20 14:44 ` Ulrich Weigand
2023-01-27 14:40 ` Aditya Kamath1
2023-01-30 19:54 ` Tom Tromey
2023-02-02 6:24 ` Aditya Kamath1
2023-02-02 6:35 ` Aditya Kamath1
2023-02-02 17:43 ` Ulrich Weigand
2023-02-03 11:10 ` Aditya Kamath1
2023-02-06 19:07 ` Ulrich Weigand
2023-02-07 11:57 ` Aditya Kamath1
2023-02-08 18:44 ` Ulrich Weigand
2023-02-10 16:33 ` Aditya Kamath1
2023-02-10 16:46 ` Aditya Kamath1
2023-02-13 19:01 ` Ulrich Weigand
2023-02-14 14:13 ` Aditya Kamath1
2023-02-16 19:46 ` Ulrich Weigand
2023-02-17 11:26 ` Aditya Kamath1
2023-02-17 12:04 ` Ulrich Weigand
2023-02-17 13:22 ` Aditya Kamath1
2023-02-17 14:18 ` Ulrich Weigand
2023-02-17 15:15 ` Aditya Kamath1
2023-02-17 19:14 ` Ulrich Weigand
2022-11-08 12:00 Aditya Kamath1
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