diff options
author | Rusty Russell <rusty@rustcorp.com.au> | 2010-04-09 08:51:01 +1000 |
---|---|---|
committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2010-04-09 08:51:01 +1000 |
commit | 606b1348af2ebc837a3876134c173c3aec6dc161 (patch) | |
tree | fa2136de59918f2f3abbfc24340be8550419170f /kernel | |
parent | 897502644ea7683b51860b8d8a2b4f1d5fbb5405 (diff) |
module:drop-lock-while-waiting
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>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/module.c | 59 |
1 files changed, 37 insertions, 22 deletions
diff --git a/kernel/module.c b/kernel/module.c index 1016b75b026a..fd8c4297432b 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -560,33 +560,26 @@ 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 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); + if (b == NULL || already_uses(a, b)) return 0; - } - /* If strong_try_module_get() returned a different error, we fail. */ + /* If we're interrupted or time out, 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); @@ -890,7 +883,7 @@ 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); @@ -1061,17 +1054,39 @@ 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; - } - return sym; + 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; } /* |