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Subject[PATCH 3/6] ipmi: use a tasklet for handling received messages
Date
The IPMI driver would release a lock, deliver a message, then relock.
This is obviously ugly, and this patch converts the message handler
interface to use a tasklet to schedule work. This lets the receive
handler be called from an interrupt handler with interrupts enabled.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
---
drivers/char/ipmi/ipmi_msghandler.c | 141 +++++++++++++++++++++--------------
drivers/char/ipmi/ipmi_si_intf.c | 14 +---
2 files changed, 88 insertions(+), 67 deletions(-)
diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 58c0e63..289ab50 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -46,6 +46,7 @@
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/rcupdate.h>
+#include <linux/interrupt.h>

#define PFX "IPMI message handler: "

@@ -53,6 +54,8 @@

static struct ipmi_recv_msg *ipmi_alloc_recv_msg(void);
static int ipmi_init_msghandler(void);
+static void smi_recv_tasklet(unsigned long);
+static void handle_new_recv_msgs(ipmi_smi_t intf);

static int initialized;

@@ -355,12 +358,15 @@ struct ipmi_smi {
int curr_seq;

/*
- * Messages that were delayed for some reason (out of memory,
- * for instance), will go in here to be processed later in a
- * periodic timer interrupt.
+ * Messages queued for delivery. If delivery fails (out of memory
+ * for instance), They will stay in here to be processed later in a
+ * periodic timer interrupt. The tasklet is for handling received
+ * messages directly from the handler.
*/
spinlock_t waiting_msgs_lock;
struct list_head waiting_msgs;
+ atomic_t watchdog_pretimeouts_to_deliver;
+ struct tasklet_struct recv_tasklet;

/*
* The list of command receivers that are registered for commands
@@ -493,6 +499,8 @@ static void clean_up_interface_data(ipmi_smi_t intf)
struct cmd_rcvr *rcvr, *rcvr2;
struct list_head list;

+ tasklet_kill(&intf->recv_tasklet);
+
free_smi_msg_list(&intf->waiting_msgs);
free_recv_msg_list(&intf->waiting_events);

@@ -2792,6 +2800,9 @@ void ipmi_poll_interface(ipmi_user_t user)

if (intf->handlers->poll)
intf->handlers->poll(intf->send_info);
+
+ /* In case something came in */
+ handle_new_recv_msgs(intf);
}
EXPORT_SYMBOL(ipmi_poll_interface);

@@ -2860,6 +2871,10 @@ int ipmi_register_smi(struct ipmi_smi_handlers *handlers,
#endif
spin_lock_init(&intf->waiting_msgs_lock);
INIT_LIST_HEAD(&intf->waiting_msgs);
+ tasklet_init(&intf->recv_tasklet,
+ smi_recv_tasklet,
+ (unsigned long) intf);
+ atomic_set(&intf->watchdog_pretimeouts_to_deliver, 0);
spin_lock_init(&intf->events_lock);
INIT_LIST_HEAD(&intf->waiting_events);
intf->waiting_events_count = 0;
@@ -3622,11 +3637,11 @@ static int handle_bmc_rsp(ipmi_smi_t intf,
}

/*
- * Handle a new message. Return 1 if the message should be requeued,
+ * Handle a received message. Return 1 if the message should be requeued,
* 0 if the message should be freed, or -1 if the message should not
* be freed or requeued.
*/
-static int handle_new_recv_msg(ipmi_smi_t intf,
+static int handle_one_recv_msg(ipmi_smi_t intf,
struct ipmi_smi_msg *msg)
{
int requeue;
@@ -3784,12 +3799,72 @@ static int handle_new_recv_msg(ipmi_smi_t intf,
return requeue;
}

+/*
+ * If there are messages in the queue or pretimeouts, handle them.
+ */
+static void handle_new_recv_msgs(ipmi_smi_t intf)
+{
+ struct ipmi_smi_msg *smi_msg;
+ unsigned long flags = 0;
+ int rv;
+ int run_to_completion = intf->run_to_completion;
+
+ /* See if any waiting messages need to be processed. */
+ if (!run_to_completion)
+ spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
+ while (!list_empty(&intf->waiting_msgs)) {
+ smi_msg = list_entry(intf->waiting_msgs.next,
+ struct ipmi_smi_msg, link);
+ list_del(&smi_msg->link);
+ if (!run_to_completion)
+ spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
+ rv = handle_one_recv_msg(intf, smi_msg);
+ if (!run_to_completion)
+ spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
+ if (rv == 0) {
+ /* Message handled */
+ ipmi_free_smi_msg(smi_msg);
+ } else if (rv < 0) {
+ /* Fatal error on the message, del but don't free. */
+ } else {
+ /*
+ * To preserve message order, quit if we
+ * can't handle a message.
+ */
+ list_add(&smi_msg->link, &intf->waiting_msgs);
+ break;
+ }
+ }
+ if (!run_to_completion)
+ spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
+
+ /*
+ * If the pretimout count is non-zero, decrement one from it and
+ * deliver pretimeouts to all the users.
+ */
+ if (atomic_add_unless(&intf->watchdog_pretimeouts_to_deliver, -1, 0)) {
+ ipmi_user_t user;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(user, &intf->users, link) {
+ if (user->handler->ipmi_watchdog_pretimeout)
+ user->handler->ipmi_watchdog_pretimeout(
+ user->handler_data);
+ }
+ rcu_read_unlock();
+ }
+}
+
+static void smi_recv_tasklet(unsigned long val)
+{
+ handle_new_recv_msgs((ipmi_smi_t) val);
+}
+
/* Handle a new message from the lower layer. */
void ipmi_smi_msg_received(ipmi_smi_t intf,
struct ipmi_smi_msg *msg)
{
unsigned long flags = 0; /* keep us warning-free. */
- int rv;
int run_to_completion;


@@ -3843,31 +3918,11 @@ void ipmi_smi_msg_received(ipmi_smi_t intf,
run_to_completion = intf->run_to_completion;
if (!run_to_completion)
spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
- if (!list_empty(&intf->waiting_msgs)) {
- list_add_tail(&msg->link, &intf->waiting_msgs);
- if (!run_to_completion)
- spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
- goto out;
- }
+ list_add_tail(&msg->link, &intf->waiting_msgs);
if (!run_to_completion)
spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);

- rv = handle_new_recv_msg(intf, msg);
- if (rv > 0) {
- /*
- * Could not handle the message now, just add it to a
- * list to handle later.
- */
- run_to_completion = intf->run_to_completion;
- if (!run_to_completion)
- spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
- list_add_tail(&msg->link, &intf->waiting_msgs);
- if (!run_to_completion)
- spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
- } else if (rv == 0) {
- ipmi_free_smi_msg(msg);
- }
-
+ tasklet_schedule(&intf->recv_tasklet);
out:
return;
}
@@ -3875,16 +3930,8 @@ EXPORT_SYMBOL(ipmi_smi_msg_received);

void ipmi_smi_watchdog_pretimeout(ipmi_smi_t intf)
{
- ipmi_user_t user;
-
- rcu_read_lock();
- list_for_each_entry_rcu(user, &intf->users, link) {
- if (!user->handler->ipmi_watchdog_pretimeout)
- continue;
-
- user->handler->ipmi_watchdog_pretimeout(user->handler_data);
- }
- rcu_read_unlock();
+ atomic_set(&intf->watchdog_pretimeouts_to_deliver, 1);
+ tasklet_schedule(&intf->recv_tasklet);
}
EXPORT_SYMBOL(ipmi_smi_watchdog_pretimeout);

@@ -3998,28 +4045,12 @@ static void ipmi_timeout_handler(long timeout_period)
ipmi_smi_t intf;
struct list_head timeouts;
struct ipmi_recv_msg *msg, *msg2;
- struct ipmi_smi_msg *smi_msg, *smi_msg2;
unsigned long flags;
int i;

rcu_read_lock();
list_for_each_entry_rcu(intf, &ipmi_interfaces, link) {
- /* See if any waiting messages need to be processed. */
- spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
- list_for_each_entry_safe(smi_msg, smi_msg2,
- &intf->waiting_msgs, link) {
- if (!handle_new_recv_msg(intf, smi_msg)) {
- list_del(&smi_msg->link);
- ipmi_free_smi_msg(smi_msg);
- } else {
- /*
- * To preserve message order, quit if we
- * can't handle a message.
- */
- break;
- }
- }
- spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
+ tasklet_schedule(&intf->recv_tasklet);

/*
* Go through the seq table and find any messages that
diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index 73ebbb1..01e53cd 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -320,16 +320,8 @@ static int register_xaction_notifier(struct notifier_block *nb)
static void deliver_recv_msg(struct smi_info *smi_info,
struct ipmi_smi_msg *msg)
{
- /* Deliver the message to the upper layer with the lock
- released. */
-
- if (smi_info->run_to_completion) {
- ipmi_smi_msg_received(smi_info->intf, msg);
- } else {
- spin_unlock(&(smi_info->si_lock));
- ipmi_smi_msg_received(smi_info->intf, msg);
- spin_lock(&(smi_info->si_lock));
- }
+ /* Deliver the message to the upper layer. */
+ ipmi_smi_msg_received(smi_info->intf, msg);
}

static void return_hosed_msg(struct smi_info *smi_info, int cCode)
@@ -481,9 +473,7 @@ static void handle_flags(struct smi_info *smi_info)

start_clear_flags(smi_info);
smi_info->msg_flags &= ~WDT_PRE_TIMEOUT_INT;
- spin_unlock(&(smi_info->si_lock));
ipmi_smi_watchdog_pretimeout(smi_info->intf);
- spin_lock(&(smi_info->si_lock));
} else if (smi_info->msg_flags & RECEIVE_MSG_AVAIL) {
/* Messages available. */
smi_info->curr_msg = ipmi_alloc_smi_msg();
--
1.7.4.1


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