On Tue, Dec 29, 2020 at 01:42:57PM +0100, Otto Moerbeek wrote:
> On Tue, Dec 29, 2020 at 12:46:54PM +0100, Mark Kettenis wrote:
>
> > > Date: Tue, 29 Dec 2020 12:21:25 +0100
> > > From: Otto Moerbeek <o...@drijf.net>
> > >
> > > Hi,
> > >
> > > this is a continuation from the threads on bugs@
> > >
> > > This version makes it explicit to *only* setup "TLS" (which actually
> > > is just a pointer to static data) with the data provided if we're
> > > running single threaded (ie.. no -pthread or -pthread but no pthread
> > > function that triggers multi-threaded init called yet). In all other
> > > cases the real allocated TLS is zero'ed. This avoids the setup issue
> > > asr is having. This diff also makes sure asr uses a specialized
> > > destructor for it's TLS to kill a mem leak that occurs on thread
> > > destruction.
> > >
> > > All in all I'm still a bit fond of the constructor approach to
> > > librthread init: it makes the distinction between having a single
> > > thread and being the main thread in a multi-threaded setup moot.
> > >
> > > Anyway, we can consider that later, please test this.
> >
> > This isn't right. The memcpy() call you're removing is there such
> > that the contents of the per-thread storage for the initial (main)
> > thread remains the same.
> >
> > With your change it reverts back to zero when the first thread is
> > created. In the particular case at hand that means the initial thread
> > would get a fresh resolver context at that point.
>
> Yes, but if I do not that crashes happen on destruct. Note that your
> initial suggestion (in asr.c)
>
> if (priv != &_asr && *priv == _asr)
> *priv = NULL;
>
> has the same property: it clears the contents if they happen to be the
> same as _asr.
>
> The crash happens if the pre-mt (static) and the TLS of the main
> thread share the same data. I did not find a way to make that work, so
> I decided to use the big hammer. I might be overlooking something
> obvious though...
This workds better, checking the flags does not work if the thread is
already on the road to desctruction.
-Otto
Index: asr/asr.c
===================================================================
RCS file: /cvs/src/lib/libc/asr/asr.c,v
retrieving revision 1.64
diff -u -p -r1.64 asr.c
--- asr/asr.c 6 Jul 2020 13:33:05 -0000 1.64
+++ asr/asr.c 29 Dec 2020 15:05:45 -0000
@@ -117,7 +117,7 @@ _asr_resolver_done(void *arg)
_asr_ctx_unref(ac);
return;
} else {
- priv = _THREAD_PRIVATE(_asr, _asr, &_asr);
+ priv = _THREAD_PRIVATE_DT(_asr, _asr, NULL, &_asr);
if (*priv == NULL)
return;
asr = *priv;
@@ -128,6 +128,23 @@ _asr_resolver_done(void *arg)
free(asr);
}
+static void
+_asr_resolver_done_tp(void *arg)
+{
+ char buf[100];
+ int len;
+ struct asr **priv = arg;
+ struct asr *asr;
+
+ if (*priv == NULL)
+ return;
+ asr = *priv;
+
+ _asr_ctx_unref(asr->a_ctx);
+ free(asr);
+ free(priv);
+}
+
void *
asr_resolver_from_string(const char *str)
{
@@ -349,7 +366,8 @@ _asr_use_resolver(void *arg)
}
else {
DPRINT("using thread-local resolver\n");
- priv = _THREAD_PRIVATE(_asr, _asr, &_asr);
+ priv = _THREAD_PRIVATE_DT(_asr, _asr, _asr_resolver_done_tp,
+ &_asr);
if (*priv == NULL) {
DPRINT("setting up thread-local resolver\n");
*priv = _asr_resolver();
Index: include/thread_private.h
===================================================================
RCS file: /cvs/src/lib/libc/include/thread_private.h,v
retrieving revision 1.35
diff -u -p -r1.35 thread_private.h
--- include/thread_private.h 13 Feb 2019 13:22:14 -0000 1.35
+++ include/thread_private.h 29 Dec 2020 15:05:45 -0000
@@ -98,7 +98,8 @@ struct thread_callbacks {
void (*tc_mutex_destroy)(void **);
void (*tc_tag_lock)(void **);
void (*tc_tag_unlock)(void **);
- void *(*tc_tag_storage)(void **, void *, size_t, void *);
+ void *(*tc_tag_storage)(void **, void *, size_t, void (*)(void *),
+ void *);
__pid_t (*tc_fork)(void);
__pid_t (*tc_vfork)(void);
void (*tc_thread_release)(struct pthread *);
@@ -142,6 +143,7 @@ __END_HIDDEN_DECLS
#define _THREAD_PRIVATE_MUTEX_LOCK(name) do {} while (0)
#define _THREAD_PRIVATE_MUTEX_UNLOCK(name) do {} while (0)
#define _THREAD_PRIVATE(keyname, storage, error) &(storage)
+#define _THREAD_PRIVATE_DT(keyname, storage, dt, error) &(storage)
#define _MUTEX_LOCK(mutex) do {} while (0)
#define _MUTEX_UNLOCK(mutex) do {} while (0)
#define _MUTEX_DESTROY(mutex) do {} while (0)
@@ -168,7 +170,12 @@ __END_HIDDEN_DECLS
#define _THREAD_PRIVATE(keyname, storage, error) \
(_thread_cb.tc_tag_storage == NULL ? &(storage) : \
_thread_cb.tc_tag_storage(&(__THREAD_NAME(keyname)), \
- &(storage), sizeof(storage), error))
+ &(storage), sizeof(storage), NULL, (error)))
+
+#define _THREAD_PRIVATE_DT(keyname, storage, dt, error)
\
+ (_thread_cb.tc_tag_storage == NULL ? &(storage) : \
+ _thread_cb.tc_tag_storage(&(__THREAD_NAME(keyname)), \
+ &(storage), sizeof(storage), (dt), (error)))
/*
* Macros used in libc to access mutexes.
Index: thread/rthread_cb.h
===================================================================
RCS file: /cvs/src/lib/libc/thread/rthread_cb.h,v
retrieving revision 1.2
diff -u -p -r1.2 rthread_cb.h
--- thread/rthread_cb.h 5 Sep 2017 02:40:54 -0000 1.2
+++ thread/rthread_cb.h 29 Dec 2020 15:05:45 -0000
@@ -35,5 +35,5 @@ void _thread_mutex_unlock(void **);
void _thread_mutex_destroy(void **);
void _thread_tag_lock(void **);
void _thread_tag_unlock(void **);
-void *_thread_tag_storage(void **, void *, size_t, void *);
+void *_thread_tag_storage(void **, void *, size_t, void (*)(void*), void *);
__END_HIDDEN_DECLS
Index: thread/rthread_libc.c
===================================================================
RCS file: /cvs/src/lib/libc/thread/rthread_libc.c,v
retrieving revision 1.3
diff -u -p -r1.3 rthread_libc.c
--- thread/rthread_libc.c 10 Jan 2019 18:45:33 -0000 1.3
+++ thread/rthread_libc.c 29 Dec 2020 15:05:45 -0000
@@ -5,6 +5,8 @@
#include <pthread.h>
#include <stdlib.h>
#include <string.h>
+#include <tib.h>
+#include <unistd.h>
#include "rthread.h"
#include "rthread_cb.h"
@@ -31,7 +33,7 @@ static pthread_mutex_t _thread_tag_mutex
* This function will never return NULL.
*/
static void
-_thread_tag_init(void **tag)
+_thread_tag_init(void **tag, void (*dt)(void *))
{
struct _thread_tag *tt;
int result;
@@ -42,7 +44,8 @@ _thread_tag_init(void **tag)
tt = malloc(sizeof *tt);
if (tt != NULL) {
result = pthread_mutex_init(&tt->m, NULL);
- result |= pthread_key_create(&tt->k, free);
+ result |= pthread_key_create(&tt->k, dt ? dt :
+ free);
*tag = tt;
}
}
@@ -62,7 +65,7 @@ _thread_tag_lock(void **tag)
if (__isthreaded) {
if (*tag == NULL)
- _thread_tag_init(tag);
+ _thread_tag_init(tag, NULL);
tt = *tag;
if (pthread_mutex_lock(&tt->m) != 0)
_rthread_debug(1, "tag mutex lock failure");
@@ -79,7 +82,7 @@ _thread_tag_unlock(void **tag)
if (__isthreaded) {
if (*tag == NULL)
- _thread_tag_init(tag);
+ _thread_tag_init(tag, NULL);
tt = *tag;
if (pthread_mutex_unlock(&tt->m) != 0)
_rthread_debug(1, "tag mutex unlock failure");
@@ -88,28 +91,33 @@ _thread_tag_unlock(void **tag)
/*
* return the thread specific data for the given tag. If there
- * is no data for this thread initialize it from 'storage'.
+ * is no data for this thread allocate and initialize it from 'storage'
+ * or clear it for non-main threads.
* On any error return 'err'.
*/
void *
-_thread_tag_storage(void **tag, void *storage, size_t sz, void *err)
+_thread_tag_storage(void **tag, void * storage, size_t sz, void (*dt)(void *),
+ void *err)
{
struct _thread_tag *tt;
void *ret;
if (*tag == NULL)
- _thread_tag_init(tag);
+ _thread_tag_init(tag, dt);
tt = *tag;
ret = pthread_getspecific(tt->k);
if (ret == NULL) {
- ret = malloc(sz);
+ ret = calloc(1, sz);
if (ret == NULL)
ret = err;
else {
- if (pthread_setspecific(tt->k, ret) == 0)
- memcpy(ret, storage, sz);
- else {
+ int len;
+ char buf[100];
+ if (pthread_setspecific(tt->k, ret) == 0) {
+ if (pthread_self() == &_initial_thread)
+ memcpy(ret, storage, sz);
+ } else {
free(ret);
ret = err;
}
