[CRYPTO] hifn: Schedule callback invocation to tasklet.

This patch forces HIFN driver to invoke crypto request callbacks from
tasklet (softirq context) instead of hardirq context, since network
stack expects it to be called from bottom halves.

It is done by simply scheduling callback invocation via dedicated
tasklet. Workqueue solution was dropped because of tooo slow
rescheduling performance (7 times slower than tasklet, for mode details
one can check this link:
http://tservice.net.ru/~s0mbre/blog/devel/other/2007_11_09.html).

Driver passed all AES and DES tests in tcryt.c module.
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/hifn_795x.c

@@ -26,6 +26,7 @@
 #include <linux/delay.h>
 #include <linux/mm.h>
 #include <linux/highmem.h>
+#include <linux/interrupt.h>
 #include <linux/crypto.h>
 
 #include <crypto/algapi.h>
@@ -426,6 +427,8 @@ struct hifn_device
 
 	u8			snum;
 
+	struct tasklet_struct	tasklet;
+
 	struct crypto_queue 	queue;
 	struct list_head	alg_list;
 };
@@ -1879,7 +1882,7 @@ static irqreturn_t hifn_interrupt(int irq, void *data)
 		hifn_write_1(dev, HIFN_1_DMA_IER, dev->dmareg);
 	}
 
-	hifn_check_for_completion(dev, 0);
+	tasklet_schedule(&dev->tasklet);
 	hifn_clear_rings(dev);
 
 	return IRQ_HANDLED;
@@ -2408,6 +2411,19 @@ static int hifn_register_alg(struct hifn_device *dev)
 	return err;
 }
 
+static void hifn_tasklet_callback(unsigned long data)
+{
+	struct hifn_device *dev = (struct hifn_device *)data;
+
+	/*
+	 * This is ok to call this without lock being held,
+	 * althogh it modifies some parameters used in parallel,
+	 * (like dev->success), but they are used in process
+	 * context or update is atomic (like setting dev->sa[i] to NULL).
+	 */
+	hifn_check_for_completion(dev, 0);
+}
+
 static int hifn_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 {
 	int err, i;
@@ -2489,6 +2505,8 @@ static int hifn_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 
 	pci_set_drvdata(pdev, dev);
 
+	tasklet_init(&dev->tasklet, hifn_tasklet_callback, (unsigned long)dev);
+
 	crypto_init_queue(&dev->queue, 1);
 
 	err = request_irq(dev->irq, hifn_interrupt, IRQF_SHARED, dev->name, dev);
@@ -2524,6 +2542,7 @@ static int hifn_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	hifn_stop_device(dev);
 err_out_free_irq:
 	free_irq(dev->irq, dev->name);
+	tasklet_kill(&dev->tasklet);
 err_out_free_desc:
 	pci_free_consistent(pdev, sizeof(struct hifn_dma),
 			dev->desc_virt, dev->desc_dma);
@@ -2563,6 +2582,7 @@ static void hifn_remove(struct pci_dev *pdev)
 		hifn_stop_device(dev);
 
 		free_irq(dev->irq, dev->name);
+		tasklet_kill(&dev->tasklet);
 
 		hifn_flush(dev);