Revert "module: drop the lock while waiting for module to complete initialization."

This reverts commit 480b02df3aa9f07d1c7df0cd8be7a5ca73893455, since
Rafael reports that it causes occasional kernel paging request faults in
load_module().

Dropping the module lock and re-taking it deep in the call-chain is
definitely not the right thing to do.  That just turns the mutex from a
lock into a "random non-locking data structure" that doesn't actually
protect what it's supposed to protect.

Requested-and-tested-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Brandon Philips <brandon@ifup.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 37 deletions

diff --git a/kernel/module.c b/kernel/module.c
index 625985e70e9d..333fbcc96978 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -563,26 +563,33 @@ int use_module(struct module *a, struct module *b)
         struct module_use *use;
         int no_warn, err;
 
-        if (b == NULL || already_uses(a, b))
-                return 0;
+        if (b == NULL || already_uses(a, b)) return 1;
 
         /* If we're interrupted or time out, we fail. */
-        err = strong_try_module_get(b);
+        if (wait_event_interruptible_timeout(
+                    module_wq, (err = strong_try_module_get(b)) != -EBUSY,
+                    30 * HZ) <= 0) {
+                printk("%s: gave up waiting for init of module %s.\n",
+                       a->name, b->name);
+                return 0;
+        }
+
+        /* If strong_try_module_get() returned a different error, we fail. */
         if (err)
-                return err;
+                return 0;
 
         DEBUGP("Allocating new usage for %s.\n", a->name);
         use = kmalloc(sizeof(*use), GFP_ATOMIC);
         if (!use) {
                 printk("%s: out of memory loading\n", a->name);
                 module_put(b);
-                return -ENOMEM;
+                return 0;
         }
 
         use->module_which_uses = a;
         list_add(&use->list, &b->modules_which_use_me);
         no_warn = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
-        return 0;
+        return 1;
 }
 EXPORT_SYMBOL_GPL(use_module);
 
@@ -875,7 +882,7 @@ static inline void module_unload_free(struct module *mod)
 
 int use_module(struct module *a, struct module *b)
 {
-        return strong_try_module_get(b);
+        return strong_try_module_get(b) == 0;
 }
 EXPORT_SYMBOL_GPL(use_module);
 
@@ -1046,39 +1053,17 @@ static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs,
         struct module *owner;
         const struct kernel_symbol *sym;
         const unsigned long *crc;
-        DEFINE_WAIT(wait);
-        int err;
-        long timeleft = 30 * HZ;
 
-again:
         sym = find_symbol(name, &owner, &crc,
                           !(mod->taints & (1 << TAINT_PROPRIETARY_MODULE)), true);
-        if (!sym)
-                return NULL;
-
-        if (!check_version(sechdrs, versindex, name, mod, crc, owner))
-                return NULL;
-
-        prepare_to_wait(&module_wq, &wait, TASK_INTERRUPTIBLE);
-        err = use_module(mod, owner);
-        if (likely(!err) || err != -EBUSY || signal_pending(current)) {
-                finish_wait(&module_wq, &wait);
-                return err ? NULL : sym;
-        }
-
-        /* Module is still loading.  Drop lock and wait. */
-        mutex_unlock(&module_mutex);
-        timeleft = schedule_timeout(timeleft);
-        mutex_lock(&module_mutex);
-        finish_wait(&module_wq, &wait);
-
-        /* Module might be gone entirely, or replaced.  Re-lookup. */
-        if (timeleft)
-                goto again;
-
-        printk(KERN_WARNING "%s: gave up waiting for init of module %s.\n",
-               mod->name, owner->name);
-        return NULL;
+        /* use_module can fail due to OOM,
+           or module initialization or unloading */
+        if (sym) {
+                if (!check_version(sechdrs, versindex, name, mod, crc, owner)
+                    || !use_module(mod, owner))
+                        sym = NULL;
+        }
+        return sym;
 }
 
 /*