From c6543a796c8b560b06cb1d53fad9ffa3906df111 Mon Sep 17 00:00:00 2001
From: Paul Selkirk <paul@psgd.org>
Date: Thu, 25 May 2017 16:09:46 -0400
Subject: Add task_yield_maybe

---
 ecdsa.c        | 1 +
 hal_internal.h | 1 +
 locks.c        | 5 +++++
 pbkdf2.c       | 9 ++-------
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/ecdsa.c b/ecdsa.c
index 27c4c2e..b9b14d8 100644
--- a/ecdsa.c
+++ b/ecdsa.c
@@ -707,6 +707,7 @@ static hal_error_t point_scalar_multiply(const fp_int * const k,
     point_double (M[1],        M[1],    curve);
     point_add    (M[bit],  P,  M[bit],  curve);
 
+    hal_task_yield_maybe();
   }
 
   /*
diff --git a/hal_internal.h b/hal_internal.h
index 3aadb48..461feec 100644
--- a/hal_internal.h
+++ b/hal_internal.h
@@ -98,6 +98,7 @@ extern void hal_critical_section_end(void);
 extern void hal_ks_lock(void);
 extern void hal_ks_unlock(void);
 extern void hal_task_yield(void);
+extern void hal_task_yield_maybe(void);
 
 /*
  * Thread sleep.  Currently used only for bad-PIN delays.
diff --git a/locks.c b/locks.c
index 9b81769..72af43b 100644
--- a/locks.c
+++ b/locks.c
@@ -106,6 +106,11 @@ WEAK_FUNCTION void hal_task_yield(void)
   return;
 }
 
+WEAK_FUNCTION void hal_task_yield_maybe(void)
+{
+  return;
+}
+
 /*
  * Local variables:
  * indent-tabs-mode: nil
diff --git a/pbkdf2.c b/pbkdf2.c
index 690831f..aa30bb5 100644
--- a/pbkdf2.c
+++ b/pbkdf2.c
@@ -108,13 +108,6 @@ hal_error_t hal_pbkdf2(hal_core_t *core,
   memset(result, 0, sizeof(result));
   memset(mac,    0, sizeof(mac));
 
-#if 1
-  /* HACK - find the second sha256 core, to avoid interfering with rpc.
-   */
-  core = hal_core_find(descriptor->core_name, NULL);
-  core = hal_core_find(descriptor->core_name, core);
-#endif
-
   /*
    * We probably should check here to see whether the password is
    * longer than the HMAC block size, and, if so, we should hash the
@@ -148,6 +141,8 @@ hal_error_t hal_pbkdf2(hal_core_t *core,
 
     for (iteration = 2; iteration <= iterations_desired; iteration++) {
 
+      hal_task_yield_maybe();
+
       if ((err = do_hmac(core, descriptor, password, password_length,
                          mac, descriptor->digest_length,
                          0, mac, sizeof(mac))) != HAL_OK)
-- 
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