Re: Debugging FreeBSD user threads with gdb
On Fri, 7 May 1999, Matthew Dillon wrote:
> :> :--- uthread_create.c 1999/03/23 05:07:55 1.12
> :> :+++ uthread_create.c 1999/05/06 15:27:33
> :> :@@ -42,6 +42,8 @@
> :> : #include "pthread_private.h"
> :> : #include "libc_private.h"
> :> :
> :> :+static int next_tid = 1;
> :> :+
> :> : int
> :> : pthread_create(pthread_t * thread, const pthread_attr_t * attr,
> :> : void *(*start_routine) (void *), void *arg)
> :> :@@ -87,6 +89,7 @@
> :> : } else {
> :> : /* Initialise the thread structure: */
> :> : memset(new_thread, 0, sizeof(struct pthread));
> :> :+ new_thread->tid = next_tid++;
> :> :
> :> :Doug Rabson Mail: d...@nlsystems.com
> :> :Nonlinear Systems Ltd.Phone: +44 181 442 9037
> :>
> :> Hmmm. tid is only an int and some programs which create and destroy
> :> threads a lot are almost certainly going to overflow it. 4 billion
> :> is not hard to reach. This can result in duplicate tid's.
> :
> :Didn't think of that. It gets a bit ugly inside gdb since gdb needs a
> :single int to encode the pid and thread id. I'm currently allowing 20
> :bits for the pid and 11 for the tid. Any ideas?
> :
> :--
> :Doug Rabson Mail: d...@nlsystems.com
> :Nonlinear Systems Ltd. Phone: +44 181 442 9037
>
> Hmmm. 11 bits is only 2048 threads. You are going to have problems
> no matter what.
>
> You could have a pool of tid structures. A simple freelist. Pseudo
> code below. This would fix the unique-tid problem but it would not fix
> the 2048 thread limit with gdb.
I can probably increase the field size of the tid up to about 14 bits (we
only have pids going up to 10 I think). I would rather not do this
amount of work inside uthread; perhaps it would be better to make the
uthread store a 64bit unique number and then compress it down to a 14 bit
tid inside gdb by keeping a hash table or something similar.
Its going to be pretty hard to debug a program with 16k active threads so
I think this limit should be ok.
--
Doug Rabson Mail: d...@nlsystems.com
Nonlinear Systems Ltd. Phone: +44 181 442 9037
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Re: Debugging FreeBSD user threads with gdb
:> :--- uthread_create.c1999/03/23 05:07:55 1.12
:> :+++ uthread_create.c1999/05/06 15:27:33
:> :@@ -42,6 +42,8 @@
:> : #include "pthread_private.h"
:> : #include "libc_private.h"
:> :
:> :+static int next_tid = 1;
:> :+
:> : int
:> : pthread_create(pthread_t * thread, const pthread_attr_t * attr,
:> : void *(*start_routine) (void *), void *arg)
:> :@@ -87,6 +89,7 @@
:> :} else {
:> :/* Initialise the thread structure: */
:> :memset(new_thread, 0, sizeof(struct pthread));
:> :+ new_thread->tid = next_tid++;
:> :
:> :Doug Rabson Mail: d...@nlsystems.com
:> :Nonlinear Systems Ltd. Phone: +44 181 442 9037
:>
:> Hmmm. tid is only an int and some programs which create and destroy
:> threads a lot are almost certainly going to overflow it. 4 billion
:> is not hard to reach. This can result in duplicate tid's.
:
:Didn't think of that. It gets a bit ugly inside gdb since gdb needs a
:single int to encode the pid and thread id. I'm currently allowing 20
:bits for the pid and 11 for the tid. Any ideas?
:
:--
:Doug RabsonMail: d...@nlsystems.com
:Nonlinear Systems Ltd. Phone: +44 181 442 9037
Hmmm. 11 bits is only 2048 threads. You are going to have problems
no matter what.
You could have a pool of tid structures. A simple freelist. Pseudo
code below. This would fix the unique-tid problem but it would not fix
the 2048 thread limit with gdb.
#define TIDINCR 32
struct tid {
struct tid *t_next;
int t_tid;
};
int maxtid = 1;
struct tid *tidpool;
struct tid *
alloctid(void)
{
struct tid *tid;
while ((tid = tidpool) == NULL) {
int i;
tidpool = malloc(sizeof(struct tid) * TIDINCR);
if (tidpool == NULL) {
... memory allocation failed ...
}
for (i = 0; i < TIDINCR; ++i) {
tidpool[i].t_tid = maxtid + i;
tidpool[i].t_next = &tidpool[i+1];
}
tidpool[i-1].t_next = NULL;
maxtid += TIDINCR;
}
tidpool = tid->t_next;
return(tid);
}
freetid(struct tid *tid)
{
tid->t_next = tidpool;
tidpool = tid;
}
-Matt
Matthew Dillon
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Re: Debugging FreeBSD user threads with gdb
On Fri, 7 May 1999, Matthew Dillon wrote:
> :--- uthread_create.c 1999/03/23 05:07:55 1.12
> :+++ uthread_create.c 1999/05/06 15:27:33
> :@@ -42,6 +42,8 @@
> : #include "pthread_private.h"
> : #include "libc_private.h"
> :
> :+static int next_tid = 1;
> :+
> : int
> : pthread_create(pthread_t * thread, const pthread_attr_t * attr,
> :void *(*start_routine) (void *), void *arg)
> :@@ -87,6 +89,7 @@
> : } else {
> : /* Initialise the thread structure: */
> : memset(new_thread, 0, sizeof(struct pthread));
> :+new_thread->tid = next_tid++;
> :
> :Doug Rabson Mail: d...@nlsystems.com
> :Nonlinear Systems Ltd. Phone: +44 181 442 9037
>
> Hmmm. tid is only an int and some programs which create and destroy
> threads a lot are almost certainly going to overflow it. 4 billion
> is not hard to reach. This can result in duplicate tid's.
Didn't think of that. It gets a bit ugly inside gdb since gdb needs a
single int to encode the pid and thread id. I'm currently allowing 20
bits for the pid and 11 for the tid. Any ideas?
--
Doug Rabson Mail: d...@nlsystems.com
Nonlinear Systems Ltd. Phone: +44 181 442 9037
To Unsubscribe: send mail to majord...@freebsd.org
with "unsubscribe freebsd-current" in the body of the message
Re: Debugging FreeBSD user threads with gdb
Matthew Dillon once wrote: > Hmmm. tid is only an int and some programs which create and destroy > threads a lot are almost certainly going to overflow it. 4 billion > is not hard to reach. This can result in duplicate tid's. Unsigned will double that. Not enough either? -mi To Unsubscribe: send mail to majord...@freebsd.org with "unsubscribe freebsd-current" in the body of the message
Re: Debugging FreeBSD user threads with gdb
:--- uthread_create.c 1999/03/23 05:07:55 1.12
:+++ uthread_create.c 1999/05/06 15:27:33
:@@ -42,6 +42,8 @@
: #include "pthread_private.h"
: #include "libc_private.h"
:
:+static int next_tid = 1;
:+
: int
: pthread_create(pthread_t * thread, const pthread_attr_t * attr,
: void *(*start_routine) (void *), void *arg)
:@@ -87,6 +89,7 @@
: } else {
: /* Initialise the thread structure: */
: memset(new_thread, 0, sizeof(struct pthread));
:+ new_thread->tid = next_tid++;
:
:Doug RabsonMail: d...@nlsystems.com
:Nonlinear Systems Ltd. Phone: +44 181 442 9037
Hmmm. tid is only an int and some programs which create and destroy
threads a lot are almost certainly going to overflow it. 4 billion
is not hard to reach. This can result in duplicate tid's.
-Matt
Matthew Dillon
To Unsubscribe: send mail to majord...@freebsd.org
with "unsubscribe freebsd-current" in the body of the message
