On Sun, May 20, 2012 at 06:42:35PM +0200, Alberto Villa wrote: > On Sun, May 20, 2012 at 8:03 AM, David Xu <listlog2...@gmail.com> wrote: > > qdbus segfaults on my machine too, I tracked it down, and found the problem > > is in QT, > > it deleted current_thread_data_key, but it still uses it in some cxa hooks, > > I applied the > > following patch, and it works fine. > > Thanks for the analysis David! > > > I think the bug depends on linking order in QT library ? if the > > qthread_unix.cpp is linked > > as lastest module, the key will be deleted after all cxa hooks run, then it > > will be fine, > > otherwise, it would crash. > > Is this really possible? No, I do not think it is possible.
The only possibility for something weird happen is for atexit/__cxa_atexit
functions to be registered from another atexit function, and then we
indeed could call the newly registered function too late.
I wonder if the following hack makes any change in the observed behaviour.
diff --git a/lib/libc/stdlib/atexit.c b/lib/libc/stdlib/atexit.c
index 511172a..bab850c 100644
--- a/lib/libc/stdlib/atexit.c
+++ b/lib/libc/stdlib/atexit.c
@@ -72,6 +72,7 @@ struct atexit {
};
static struct atexit *__atexit; /* points to head of LIFO stack
*/
+static int atexit_gen;
/*
* Register the function described by 'fptr' to be called at application
@@ -107,6 +108,7 @@ atexit_register(struct atexit_fn *fptr)
__atexit = p;
}
p->fns[p->ind++] = *fptr;
+ atexit_gen++;
_MUTEX_UNLOCK(&atexit_mutex);
return 0;
}
@@ -162,7 +164,7 @@ __cxa_finalize(void *dso)
struct dl_phdr_info phdr_info;
struct atexit *p;
struct atexit_fn fn;
- int n, has_phdr;
+ int atexit_gen_prev, n, has_phdr;
if (dso != NULL)
has_phdr = _rtld_addr_phdr(dso, &phdr_info);
@@ -170,6 +172,8 @@ __cxa_finalize(void *dso)
has_phdr = 0;
_MUTEX_LOCK(&atexit_mutex);
+retry:
+ atexit_gen_prev = atexit_gen;
for (p = __atexit; p; p = p->next) {
for (n = p->ind; --n >= 0;) {
if (p->fns[n].fn_type == ATEXIT_FN_EMPTY)
@@ -196,6 +200,8 @@ __cxa_finalize(void *dso)
_MUTEX_LOCK(&atexit_mutex);
}
}
+ if (atexit_gen_prev != atexit_gen)
+ goto retry;
_MUTEX_UNLOCK(&atexit_mutex);
if (dso == NULL)
_MUTEX_DESTROY(&atexit_mutex);
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