On Tue, Jan 15, 2013 at 9:53 AM, Ming Lei <ming....@canonical.com> wrote:
>
> I will try to figure out one patch to address the scsi block async probe
> issue first, and see if it can fix the problem by moving add_disk()
> into sd_probe()
> and calling async_synchronize_full_domain(&scsi_sd_probe_domain)
> in the entry of sd_open().
Looks it isn't doable because the block partition device can only be created
inside the async things.
But I have another idea to address the problem, and let module code call
async_synchronize_full() only if the module requires that explicitly, so how
about the below draft patch?
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 7992635..c5106a0 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3143,6 +3143,8 @@ static int __init init_sd(void)
if (err)
goto err_out_driver;
+ mod_init_async_wait(THIS_MODULE);
+
return 0;
err_out_driver:
diff --git a/include/linux/module.h b/include/linux/module.h
index 7760c6d..09bd4c5 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -300,6 +300,12 @@ struct module
unsigned int taints; /* same bits as kernel:tainted */
+ /*
+ * set if the module wants to call async_synchronize_full
+ * after its init() is complted.
+ */
+ unsigned int init_async_wait:1;
+
#ifdef CONFIG_GENERIC_BUG
/* Support for BUG */
unsigned num_bugs;
@@ -656,4 +662,16 @@ static inline void module_bug_finalize(const Elf_Ehdr *hdr,
static inline void module_bug_cleanup(struct module *mod) {}
#endif /* CONFIG_GENERIC_BUG */
+/*
+ * If one module wants to complete its all async code after
+ * its init() executed, the module can call this function in
+ * the entry of its init(), but the module's async function
+ * can't call request_module, otherwise deadlock will be caused.
+ */
+static inline void mod_init_async_wait(struct module *mod)
+{
+ if (mod)
+ mod->init_async_wait = 1;
+}
+
#endif /* _LINUX_MODULE_H */
diff --git a/kernel/module.c b/kernel/module.c
index 250092c..dc5d011 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3058,8 +3058,9 @@ static int do_init_module(struct module *mod)
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_LIVE, mod);
- /* We need to finish all async code before the module init sequence is
done */
- async_synchronize_full();
+ /* Only complete all async code if the module requires that */
+ if (mod->init_async_wait)
+ async_synchronize_full();
mutex_lock(&module_mutex);
/* Drop initial reference. */
Thanks,
--
Ming Lei
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