On 24/06/16 13:30, Herbert Xu wrote:

On Wed, Jun 22, 2016 at 04:23:38PM +0300, Tero Kristo wrote:

quoted

Some of the call paths of OMAP SHA driver can avoid executing the next
step of the crypto queue under tasklet; instead, execute the next step
directly via function call. This avoids a costly round-trip via the
scheduler giving a slight performance boost.

Signed-off-by: Tero Kristo <redacted>
---
  drivers/crypto/omap-sham.c | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/crypto/omap-sham.c b/drivers/crypto/omap-sham.c
index 6247887..84a0027 100644
--- a/drivers/crypto/omap-sham.c
+++ b/drivers/crypto/omap-sham.c

@@ -242,6 +242,8 @@ static struct omap_sham_drv sham = {
  	.lock = __SPIN_LOCK_UNLOCKED(sham.lock),
  };

+static void omap_sham_done_task(unsigned long data);
+
  static inline u32 omap_sham_read(struct omap_sham_dev *dd, u32 offset)
  {
  	return __raw_readl(dd->io_base + offset);

@@ -1007,7 +1009,7 @@ static void omap_sham_finish_req(struct ahash_request *req, int err)
  		req->base.complete(&req->base, err);

  	/* handle new request */
-	tasklet_schedule(&dd->done_task);
+	omap_sham_done_task((unsigned long)dd);
  }

Hmm, what guarnatees that you won't run out of stack doing this?

Good question, I had a deeper look at the driver and it seems you are 
right... It may result in a recursion loop within the driver. I will dig 
this further and break the recursion if it indeed can call itself 
indefinitely.

My knowledge of the crypto stack (+ these drivers unfortunately) is 
still pretty limited, I appreciate your reviews a lot.

-Tero