hang in dlclose() on rtld lock (powerpc64)
Konstantin Belousov
kostikbel at gmail.com
Thu Mar 9 16:31:11 UTC 2017
On Thu, Mar 09, 2017 at 09:59:00AM -0600, Justin Hibbits wrote:
> When building ports in poudriere, I see gdk-pixbuf-query-modules and
> gio-querymodules hanging on r314676, but working in r305820. I took a
> backtrace on both in gdb, and see the following (identical between both):
>
> Program received signal SIGINT, Interrupt.
> 0x00000000506831d8 in .__sys.umtx_op () from /lib/libc.so.7
> (gdb) bt
> #0 0x00000000506831d8 in .__sys.umtx_op () from /lib/libc.so.7
> #1 0x0000000050588010 in _umtx_op_err (obj=0x4, op=13, val=0, uaddr=0x0,
> uaddr2=0x0)
> at /home/chmeee/freebsd/pristine/lib/libthr/thread/thr_umtx.c:37
> #2 0x00000000505881b8 in __thr_rwlock_wrlock (rwlock=<optimized out>,
> tsp=<optimized out>)
> at /home/chmeee/freebsd/pristine/lib/libthr/thread/thr_umtx.c:325
> #3 0x00000000505965f0 in _thr_rwlock_wrlock (tsp=<optimized out>,
> rwlock=<optimized out>)
> at /home/chmeee/freebsd/pristine/lib/libthr/thread/thr_umtx.h:239
> #4 _thr_rtld_wlock_acquire (lock=0x505bdd00)
> at /home/chmeee/freebsd/pristine/lib/libthr/thread/thr_rtld.c:141
> #5 0x0000000050026bf4 in wlock_acquire (lock=0x5004cf20 <rtld_locks>,
> lockstate=0xffffffffffffcab0)
> at /home/chmeee/freebsd/pristine/libexec/rtld-elf/rtld_lock.c:222
> #6 0x0000000050022b1c in dlclose (handle=0x51d62000)
> at /home/chmeee/freebsd/pristine/libexec/rtld-elf/rtld.c:3021
> #7 0x0000000050022c90 in free_needed_filtees (n=0x509f7420)
> at /home/chmeee/freebsd/pristine/libexec/rtld-elf/rtld.c:2113
> #8 0x0000000050022d18 in unload_filtees (obj=0x509fa800)
> at /home/chmeee/freebsd/pristine/libexec/rtld-elf/rtld.c:2129
> #9 0x0000000050022e54 in unload_object (root=<optimized out>)
> at /home/chmeee/freebsd/pristine/libexec/rtld-elf/rtld.c:4464
> #10 0x0000000050022c20 in dlclose (handle=0x50054000)
> at /home/chmeee/freebsd/pristine/libexec/rtld-elf/rtld.c:3044
> ---Type <return> to continue, or q <return> to quit---q
>
>
> This happens on powerpc64. I haven't tested on powerpc or any other arch.
Please test the following patch. It avoids recursing on the bind lock.
diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index a7c61b2d13f..880cf100c45 100644
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -77,6 +77,7 @@ static void digest_dynamic2(Obj_Entry *, const Elf_Dyn *, const Elf_Dyn *,
static void digest_dynamic(Obj_Entry *, int);
static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
static Obj_Entry *dlcheck(void *);
+static int dlclose_locked(void *, RtldLockState *);
static Obj_Entry *dlopen_object(const char *name, int fd, Obj_Entry *refobj,
int lo_flags, int mode, RtldLockState *lockstate);
static Obj_Entry *do_load_object(int, const char *, char *, struct stat *, int);
@@ -98,7 +99,7 @@ static void initlist_add_objects(Obj_Entry *, Obj_Entry *, Objlist *);
static void linkmap_add(Obj_Entry *);
static void linkmap_delete(Obj_Entry *);
static void load_filtees(Obj_Entry *, int flags, RtldLockState *);
-static void unload_filtees(Obj_Entry *);
+static void unload_filtees(Obj_Entry *, RtldLockState *);
static int load_needed_objects(Obj_Entry *, int);
static int load_preload_objects(void);
static Obj_Entry *load_object(const char *, int fd, const Obj_Entry *, int);
@@ -142,7 +143,7 @@ static int symlook_obj1_sysv(SymLook *, const Obj_Entry *);
static int symlook_obj1_gnu(SymLook *, const Obj_Entry *);
static void trace_loaded_objects(Obj_Entry *);
static void unlink_object(Obj_Entry *);
-static void unload_object(Obj_Entry *);
+static void unload_object(Obj_Entry *, RtldLockState *lockstate);
static void unref_dag(Obj_Entry *);
static void ref_dag(Obj_Entry *);
static char *origin_subst_one(Obj_Entry *, char *, const char *,
@@ -2104,13 +2105,13 @@ initlist_add_objects(Obj_Entry *obj, Obj_Entry *tail, Objlist *list)
#endif
static void
-free_needed_filtees(Needed_Entry *n)
+free_needed_filtees(Needed_Entry *n, RtldLockState *lockstate)
{
Needed_Entry *needed, *needed1;
for (needed = n; needed != NULL; needed = needed->next) {
if (needed->obj != NULL) {
- dlclose(needed->obj);
+ dlclose_locked(needed->obj, lockstate);
needed->obj = NULL;
}
}
@@ -2121,14 +2122,14 @@ free_needed_filtees(Needed_Entry *n)
}
static void
-unload_filtees(Obj_Entry *obj)
+unload_filtees(Obj_Entry *obj, RtldLockState *lockstate)
{
- free_needed_filtees(obj->needed_filtees);
- obj->needed_filtees = NULL;
- free_needed_filtees(obj->needed_aux_filtees);
- obj->needed_aux_filtees = NULL;
- obj->filtees_loaded = false;
+ free_needed_filtees(obj->needed_filtees, lockstate);
+ obj->needed_filtees = NULL;
+ free_needed_filtees(obj->needed_aux_filtees, lockstate);
+ obj->needed_aux_filtees = NULL;
+ obj->filtees_loaded = false;
}
static void
@@ -3015,15 +3016,23 @@ search_library_pathfds(const char *name, const char *path, int *fdp)
int
dlclose(void *handle)
{
+ RtldLockState lockstate;
+ int error;
+
+ wlock_acquire(rtld_bind_lock, &lockstate);
+ error = dlclose_locked(handle, &lockstate);
+ lock_release(rtld_bind_lock, &lockstate);
+ return (error);
+}
+
+static int
+dlclose_locked(void *handle, RtldLockState *lockstate)
+{
Obj_Entry *root;
- RtldLockState lockstate;
- wlock_acquire(rtld_bind_lock, &lockstate);
root = dlcheck(handle);
- if (root == NULL) {
- lock_release(rtld_bind_lock, &lockstate);
+ if (root == NULL)
return -1;
- }
LD_UTRACE(UTRACE_DLCLOSE_START, handle, NULL, 0, root->dl_refcount,
root->path);
@@ -3035,19 +3044,18 @@ dlclose(void *handle)
* The object will be no longer referenced, so we must unload it.
* First, call the fini functions.
*/
- objlist_call_fini(&list_fini, root, &lockstate);
+ objlist_call_fini(&list_fini, root, lockstate);
unref_dag(root);
/* Finish cleaning up the newly-unreferenced objects. */
GDB_STATE(RT_DELETE,&root->linkmap);
- unload_object(root);
+ unload_object(root, lockstate);
GDB_STATE(RT_CONSISTENT,NULL);
} else
unref_dag(root);
LD_UTRACE(UTRACE_DLCLOSE_STOP, handle, NULL, 0, 0, NULL);
- lock_release(rtld_bind_lock, &lockstate);
return 0;
}
@@ -3123,13 +3131,13 @@ rtld_dlopen(const char *name, int fd, int mode)
}
static void
-dlopen_cleanup(Obj_Entry *obj)
+dlopen_cleanup(Obj_Entry *obj, RtldLockState *lockstate)
{
obj->dl_refcount--;
unref_dag(obj);
if (obj->refcount == 0)
- unload_object(obj);
+ unload_object(obj, lockstate);
}
static Obj_Entry *
@@ -3178,7 +3186,7 @@ dlopen_object(const char *name, int fd, Obj_Entry *refobj, int lo_flags,
(mode & RTLD_MODEMASK) == RTLD_NOW, &obj_rtld,
(lo_flags & RTLD_LO_EARLY) ? SYMLOOK_EARLY : 0,
lockstate) == -1) {
- dlopen_cleanup(obj);
+ dlopen_cleanup(obj, lockstate);
obj = NULL;
} else if (lo_flags & RTLD_LO_EARLY) {
/*
@@ -3235,7 +3243,7 @@ dlopen_object(const char *name, int fd, Obj_Entry *refobj, int lo_flags,
(lo_flags & RTLD_LO_EARLY) ? SYMLOOK_EARLY : 0,
lockstate) == -1) {
objlist_clear(&initlist);
- dlopen_cleanup(obj);
+ dlopen_cleanup(obj, lockstate);
if (lockstate == &mlockstate)
lock_release(rtld_bind_lock, lockstate);
return (NULL);
@@ -4429,7 +4437,7 @@ trace_loaded_objects(Obj_Entry *obj)
* reference count of 0.
*/
static void
-unload_object(Obj_Entry *root)
+unload_object(Obj_Entry *root, RtldLockState *lockstate)
{
Obj_Entry marker, *obj, *next;
@@ -4461,11 +4469,11 @@ unload_object(Obj_Entry *root)
if (next != NULL) {
init_marker(&marker);
TAILQ_INSERT_BEFORE(next, &marker, next);
- unload_filtees(obj);
+ unload_filtees(obj, lockstate);
next = TAILQ_NEXT(&marker, next);
TAILQ_REMOVE(&obj_list, &marker, next);
} else
- unload_filtees(obj);
+ unload_filtees(obj, lockstate);
}
release_object(obj);
}
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