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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2016-07-25 10:43:13 +0200
committerTony Luck <tony.luck@intel.com>2016-07-25 18:55:32 +0200
commitfbb0e4da96f4503e65bc4fb627cf4e1d7c8c64e6 (patch)
tree7c17fa1f6f451a838974067ef63372818404c495 /arch/ia64
parentia64: efi: use timespec64 for persistent clock (diff)
downloadlinux-fbb0e4da96f4503e65bc4fb627cf4e1d7c8c64e6.tar.xz
linux-fbb0e4da96f4503e65bc4fb627cf4e1d7c8c64e6.zip
ia64: salinfo: use a waitqueue instead a sema down/up combo
The only purpose of down_try_lock() followed by up() seems to be to wake up a possible reader. This patch replaces it with a wake-queue. There is no locking around cpumask_empty() and the test is re-done in case there was no hit. With wait_event_interruptible_lock_irq(,&data_saved_lock) we would probably be able to get rid of the `retry` label. However we still can return CPU X which is valid now but later (after the lock dropped) the event may have been removed because the CPU went offline. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Tony Luck <tony.luck@intel.com>
Diffstat (limited to 'arch/ia64')
-rw-r--r--arch/ia64/kernel/salinfo.c38
1 files changed, 10 insertions, 28 deletions
diff --git a/arch/ia64/kernel/salinfo.c b/arch/ia64/kernel/salinfo.c
index 1eeffb7fbb16..5313007d5423 100644
--- a/arch/ia64/kernel/salinfo.c
+++ b/arch/ia64/kernel/salinfo.c
@@ -141,7 +141,7 @@ enum salinfo_state {
struct salinfo_data {
cpumask_t cpu_event; /* which cpus have outstanding events */
- struct semaphore mutex;
+ wait_queue_head_t read_wait;
u8 *log_buffer;
u64 log_size;
u8 *oemdata; /* decoded oem data */
@@ -182,21 +182,6 @@ struct salinfo_platform_oemdata_parms {
int ret;
};
-/* Kick the mutex that tells user space that there is work to do. Instead of
- * trying to track the state of the mutex across multiple cpus, in user
- * context, interrupt context, non-maskable interrupt context and hotplug cpu,
- * it is far easier just to grab the mutex if it is free then release it.
- *
- * This routine must be called with data_saved_lock held, to make the down/up
- * operation atomic.
- */
-static void
-salinfo_work_to_do(struct salinfo_data *data)
-{
- (void)(down_trylock(&data->mutex) ?: 0);
- up(&data->mutex);
-}
-
static void
salinfo_platform_oemdata_cpu(void *context)
{
@@ -258,7 +243,7 @@ salinfo_log_wakeup(int type, u8 *buffer, u64 size, int irqsafe)
}
cpumask_set_cpu(smp_processor_id(), &data->cpu_event);
if (irqsafe) {
- salinfo_work_to_do(data);
+ wake_up_interruptible(&data->read_wait);
spin_unlock_irqrestore(&data_saved_lock, flags);
}
}
@@ -271,14 +256,10 @@ extern void ia64_mlogbuf_dump(void);
static void
salinfo_timeout_check(struct salinfo_data *data)
{
- unsigned long flags;
if (!data->open)
return;
- if (!cpumask_empty(&data->cpu_event)) {
- spin_lock_irqsave(&data_saved_lock, flags);
- salinfo_work_to_do(data);
- spin_unlock_irqrestore(&data_saved_lock, flags);
- }
+ if (!cpumask_empty(&data->cpu_event))
+ wake_up_interruptible(&data->read_wait);
}
static void
@@ -308,10 +289,11 @@ salinfo_event_read(struct file *file, char __user *buffer, size_t count, loff_t
int i, n, cpu = -1;
retry:
- if (cpumask_empty(&data->cpu_event) && down_trylock(&data->mutex)) {
+ if (cpumask_empty(&data->cpu_event)) {
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
- if (down_interruptible(&data->mutex))
+ if (wait_event_interruptible(data->read_wait,
+ !cpumask_empty(&data->cpu_event)))
return -EINTR;
}
@@ -510,7 +492,7 @@ salinfo_log_clear(struct salinfo_data *data, int cpu)
if (data->state == STATE_LOG_RECORD) {
spin_lock_irqsave(&data_saved_lock, flags);
cpumask_set_cpu(cpu, &data->cpu_event);
- salinfo_work_to_do(data);
+ wake_up_interruptible(&data->read_wait);
spin_unlock_irqrestore(&data_saved_lock, flags);
}
return 0;
@@ -582,7 +564,7 @@ salinfo_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu
i < ARRAY_SIZE(salinfo_data);
++i, ++data) {
cpumask_set_cpu(cpu, &data->cpu_event);
- salinfo_work_to_do(data);
+ wake_up_interruptible(&data->read_wait);
}
spin_unlock_irqrestore(&data_saved_lock, flags);
break;
@@ -640,7 +622,7 @@ salinfo_init(void)
for (i = 0; i < ARRAY_SIZE(salinfo_log_name); i++) {
data = salinfo_data + i;
data->type = i;
- sema_init(&data->mutex, 1);
+ init_waitqueue_head(&data->read_wait);
dir = proc_mkdir(salinfo_log_name[i], salinfo_dir);
if (!dir)
continue;