[PATCH v3] ipmi:si: Add async init to ipmi_si

[Michal Clapinski <mclapinski@google.com>]

Added a new config option to allow offloading individual calls to
try_smi_init() using workqueue.

Saves 100ms on my system.

Signed-off-by: Michal Clapinski <mclapinski@google.com>
---
v3:
- removed __init from the async function
- reimplemented the whole thing with a workqueue
- added cancel_work_sync to cleanup_one_si, which means cleanup_one_si
  now has to run without the smi_infos_lock
v2:
- instead of offloading the whole init function, offload just the
  individual calls to try_smi_init()
---
 drivers/char/ipmi/Kconfig        |  9 ++++
 drivers/char/ipmi/ipmi_si_intf.c | 79 +++++++++++++++++++++++++-------
 2 files changed, 72 insertions(+), 16 deletions(-)

diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
index 669f76000197..538a7d3c65bf 100644
--- a/drivers/char/ipmi/Kconfig
+++ b/drivers/char/ipmi/Kconfig
@@ -67,6 +67,15 @@ config IPMI_SI
 	  Currently, only KCS and SMIC are supported.  If
 	  you are using IPMI, you should probably say "y" here.
 
+config IPMI_SI_ASYNC_INIT
+	bool 'Asynchronous initialization of IPMI System Interface'
+	depends on IPMI_SI
+	default n
+	help
+	  Offloads individual SMI inits. It speeds up the boot time.
+	  It also introduces a very small risk that something else might fail
+	  if it depends on synchronous IPMI init.
+
 config IPMI_SSIF
 	tristate 'IPMI SMBus handler (SSIF)'
 	depends on I2C
diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index 9a9d12be9bf7..79c510a8d00a 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -39,6 +39,7 @@
 #include <linux/rcupdate.h>
 #include <linux/ipmi.h>
 #include <linux/ipmi_smi.h>
+#include <linux/workqueue.h>
 #include "ipmi_si.h"
 #include "ipmi_si_sm.h"
 #include <linux/string.h>
@@ -252,6 +253,8 @@ struct smi_info {
 
 	struct task_struct *thread;
 
+	struct work_struct init_work;
+
 	struct list_head link;
 };
 
@@ -272,6 +275,7 @@ static bool unload_when_empty = true;
 static int try_smi_init(struct smi_info *smi);
 static void cleanup_one_si(struct smi_info *smi_info);
 static void cleanup_ipmi_si(void);
+static void smi_init_work_fn(struct work_struct *work);
 
 #ifdef DEBUG_TIMING
 void debug_timestamp(struct smi_info *smi_info, char *msg)
@@ -1970,6 +1974,7 @@ int ipmi_si_add_smi(struct si_sm_io *io)
 	if (!new_smi)
 		return -ENOMEM;
 	spin_lock_init(&new_smi->si_lock);
+	INIT_WORK(&new_smi->init_work, smi_init_work_fn);
 
 	new_smi->io = *io;
 
@@ -1982,7 +1987,12 @@ int ipmi_si_add_smi(struct si_sm_io *io)
 			dev_info(dup->io.dev,
 				 "Removing SMBIOS-specified %s state machine in favor of ACPI\n",
 				 si_to_str[new_smi->io.si_info->type]);
+			list_del(&dup->link);
+			mutex_unlock(&smi_infos_lock);
+
 			cleanup_one_si(dup);
+
+			mutex_lock(&smi_infos_lock);
 		} else {
 			dev_info(new_smi->io.dev,
 				 "%s-specified %s state machine: duplicate\n",
@@ -2000,8 +2010,12 @@ int ipmi_si_add_smi(struct si_sm_io *io)
 
 	list_add_tail(&new_smi->link, &smi_infos);
 
-	if (initialized)
-		rv = try_smi_init(new_smi);
+	if (initialized) {
+		if (IS_ENABLED(CONFIG_IPMI_SI_ASYNC_INIT))
+			queue_work(system_unbound_wq, &new_smi->init_work);
+		else
+			rv = try_smi_init(new_smi);
+	}
 out_err:
 	mutex_unlock(&smi_infos_lock);
 	return rv;
@@ -2174,6 +2188,15 @@ static bool __init ipmi_smi_info_same(struct smi_info *e1, struct smi_info *e2)
 		e1->io.addr_data == e2->io.addr_data);
 }
 
+static void smi_init_work_fn(struct work_struct *work)
+{
+	struct smi_info *smi = container_of(work, struct smi_info, init_work);
+
+	mutex_lock(&smi_infos_lock);
+	try_smi_init(smi);
+	mutex_unlock(&smi_infos_lock);
+}
+
 static int __init init_ipmi_si(void)
 {
 	struct smi_info *e, *e2;
@@ -2219,8 +2242,12 @@ static int __init init_ipmi_si(void)
 				break;
 			}
 		}
-		if (!dup)
-			try_smi_init(e);
+		if (!dup) {
+			if (IS_ENABLED(CONFIG_IPMI_SI_ASYNC_INIT))
+				queue_work(system_unbound_wq, &e->init_work);
+			else
+				try_smi_init(e);
+		}
 	}
 
 	/*
@@ -2253,8 +2280,12 @@ static int __init init_ipmi_si(void)
 				break;
 			}
 		}
-		if (!dup)
-			try_smi_init(e);
+		if (!dup) {
+			if (IS_ENABLED(CONFIG_IPMI_SI_ASYNC_INIT))
+				queue_work(system_unbound_wq, &e->init_work);
+			else
+				try_smi_init(e);
+		}
 	}
 
 	initialized = true;
@@ -2344,31 +2375,36 @@ static void shutdown_smi(void *send_info)
 }
 
 /*
- * Must be called with smi_infos_lock held, to serialize the
- * smi_info->intf check.
+ * Must be called with smi_info unlinked from smi_infos and smi_infos_lock released.
  */
 static void cleanup_one_si(struct smi_info *smi_info)
 {
 	if (!smi_info)
 		return;
 
-	list_del(&smi_info->link);
+	if (IS_ENABLED(CONFIG_IPMI_SI_ASYNC_INIT))
+		cancel_work_sync(&smi_info->init_work);
+
 	ipmi_unregister_smi(smi_info->intf);
 	kfree(smi_info);
 }
 
 void ipmi_si_remove_by_dev(struct device *dev)
 {
-	struct smi_info *e;
+	struct smi_info *e = NULL, *tmp;
 
 	mutex_lock(&smi_infos_lock);
-	list_for_each_entry(e, &smi_infos, link) {
-		if (e->io.dev == dev) {
-			cleanup_one_si(e);
+	list_for_each_entry(tmp, &smi_infos, link) {
+		if (tmp->io.dev == dev) {
+			e = tmp;
+			list_del(&e->link);
 			break;
 		}
 	}
 	mutex_unlock(&smi_infos_lock);
+
+	if (e)
+		cleanup_one_si(e);
 }
 
 struct device *ipmi_si_remove_by_data(int addr_space, enum si_type si_type,
@@ -2377,6 +2413,7 @@ struct device *ipmi_si_remove_by_data(int addr_space, enum si_type si_type,
 	/* remove */
 	struct smi_info *e, *tmp_e;
 	struct device *dev = NULL;
+	LIST_HEAD(to_clean);
 
 	mutex_lock(&smi_infos_lock);
 	list_for_each_entry_safe(e, tmp_e, &smi_infos, link) {
@@ -2386,17 +2423,23 @@ struct device *ipmi_si_remove_by_data(int addr_space, enum si_type si_type,
 			continue;
 		if (e->io.addr_data == addr) {
 			dev = get_device(e->io.dev);
-			cleanup_one_si(e);
+			list_move_tail(&e->link, &to_clean);
 		}
 	}
 	mutex_unlock(&smi_infos_lock);
 
+	list_for_each_entry_safe(e, tmp_e, &to_clean, link) {
+		list_del(&e->link);
+		cleanup_one_si(e);
+	}
+
 	return dev;
 }
 
 static void cleanup_ipmi_si(void)
 {
 	struct smi_info *e, *tmp_e;
+	LIST_HEAD(to_clean);
 
 	if (!initialized)
 		return;
@@ -2410,10 +2453,14 @@ static void cleanup_ipmi_si(void)
 	ipmi_si_platform_shutdown();
 
 	mutex_lock(&smi_infos_lock);
-	list_for_each_entry_safe(e, tmp_e, &smi_infos, link)
-		cleanup_one_si(e);
+	list_splice_init(&smi_infos, &to_clean);
 	mutex_unlock(&smi_infos_lock);
 
+	list_for_each_entry_safe(e, tmp_e, &to_clean, link) {
+		list_del(&e->link);
+		cleanup_one_si(e);
+	}
+
 	ipmi_si_hardcode_exit();
 	ipmi_si_hotmod_exit();
 }
-- 
2.55.0.654.g21b8a5bc05-goog