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

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This fixes "gave up waiting for init of module libcrc32c." which
happened at boot time due to multiple parallel module loads.

The problem was a deadlock: we wait for a module to finish
initializing, but we keep the module_lock mutex so it can't complete.
In particular, this could reasonably happen if a module does a
request_module() in its initialization routine.

So we change use_module() to return an errno rather than a bool, and if
it's -EBUSY we drop the lock and wait in the caller, then reaquire the
lock.

Reported-by: Brandon Philips <brandon@ifup.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Brandon Philips <brandon@ifup.org>
This commit is contained in:
Rusty Russell 2010-05-19 17:33:39 -06:00
parent fedb3d27d9
commit 480b02df3a
1 changed files with 36 additions and 21 deletions
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57
kernel/module.c
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@ -561,33 +561,26 @@ 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 1;
if (b == NULL || already_uses(a, b))
return 0;
/* If we're interrupted or time out, we fail. */
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. */
err = strong_try_module_get(b);
if (err)
return 0;
return err;
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 0;
return -ENOMEM;
}
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 1;
return 0;
}
EXPORT_SYMBOL_GPL(use_module);
@ -880,7 +873,7 @@ static inline void module_unload_free(struct module *mod)
int use_module(struct module *a, struct module *b)
{
return strong_try_module_get(b) == 0;
return strong_try_module_get(b);
}
EXPORT_SYMBOL_GPL(use_module);
@ -1051,17 +1044,39 @@ 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);
/* 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;
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;
}
return 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;
}
/*