[src/trunk]: src/sys/dev Simplify loops by putting interrupt test at end.

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/8005d1a55717
branches:  trunk
changeset: 1009950:8005d1a55717
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Fri May 08 15:57:24 2020 +0000

description:
Simplify loops by putting interrupt test at end.

diffstat:

 sys/dev/random.c |  66 ++++++++++++++++++-------------------------------------
 1 files changed, 22 insertions(+), 44 deletions(-)

diffs (125 lines):

diff -r 353a7abc8bf7 -r 8005d1a55717 sys/dev/random.c
--- a/sys/dev/random.c  Fri May 08 15:55:05 2020 +0000
+++ b/sys/dev/random.c  Fri May 08 15:57:24 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: random.c,v 1.5 2020/05/08 15:55:05 riastradh Exp $     */
+/*     $NetBSD: random.c,v 1.6 2020/05/08 15:57:24 riastradh Exp $     */
 
 /*-
  * Copyright (c) 2019 The NetBSD Foundation, Inc.
@@ -47,7 +47,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: random.c,v 1.5 2020/05/08 15:55:05 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: random.c,v 1.6 2020/05/08 15:57:24 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -213,7 +213,6 @@
        struct nist_hash_drbg drbg;
        uint8_t *buf;
        int extractflags;
-       bool interruptible;
        int error;
 
        /* Get a buffer for transfers.  */
@@ -258,18 +257,10 @@
        /* Promptly zero the seed.  */
        explicit_memset(seed, 0, sizeof seed);
 
-       /*
-        * Generate data.  Assume no error until failure.  No
-        * interruption at this point until we've generated at least
-        * one block of output.
-        */
+       /* Generate data.  */
        error = 0;
-       interruptible = false;
        while (uio->uio_resid) {
-               size_t n = uio->uio_resid;
-
-               /* No more than one buffer's worth.  */
-               n = MIN(n, RANDOM_BUFSIZE);
+               size_t n = MIN(uio->uio_resid, RANDOM_BUFSIZE);
 
                /*
                 * Clamp /dev/random output to the entropy capacity and
@@ -286,22 +277,6 @@
                        CTASSERT(sizeof seed <= RANDOM_BUFSIZE);
                }
 
-               /* Yield if requested.  */
-               if (curcpu()->ci_schedstate.spc_flags & SPCF_SHOULDYIELD)
-                       preempt();
-
-               /*
-                * Allow interruption, but only after providing a
-                * minimum number of bytes.
-                */
-               CTASSERT(RANDOM_BUFSIZE >= 256);
-               /* Check for interruption.  */
-               if (__predict_false(curlwp->l_flag & LW_PENDSIG) &&
-                   interruptible && sigispending(curlwp, 0)) {
-                       error = EINTR; /* XXX ERESTART? */
-                       break;
-               }
-
                /*
                 * Try to generate a block of data, but if we've hit
                 * the DRBG reseed interval, reseed.
@@ -348,11 +323,17 @@
                        break;
                }
 
-               /*
-                * We have generated one block of output, so it is
-                * reasonable to allow interruption after this point.
-                */
-               interruptible = true;
+               /* Yield if requested.  */
+               if (curcpu()->ci_schedstate.spc_flags & SPCF_SHOULDYIELD)
+                       preempt();
+
+               /* Check for interruption after at least 256 bytes.  */
+               CTASSERT(RANDOM_BUFSIZE >= 256);
+               if (__predict_false(curlwp->l_flag & LW_PENDSIG) &&
+                   sigispending(curlwp, 0)) {
+                       error = EINTR;
+                       break;
+               }
        }
 
 out:   /* Zero the buffer and free it.  */
@@ -401,10 +382,14 @@
 
        /* Consume data.  */
        while (uio->uio_resid) {
-               size_t n = uio->uio_resid;
+               size_t n = MIN(uio->uio_resid, RANDOM_BUFSIZE);
 
-               /* No more than one buffer's worth in one step.  */
-               n = MIN(uio->uio_resid, RANDOM_BUFSIZE);
+               /* Transfer n bytes in and enter them into the pool.  */
+               error = uiomove(buf, n, uio);
+               if (error)
+                       break;
+               rnd_add_data(&user_rndsource, buf, n, privileged ? n*NBBY : 0);
+               any = true;
 
                /* Yield if requested.  */
                if (curcpu()->ci_schedstate.spc_flags & SPCF_SHOULDYIELD)
@@ -416,13 +401,6 @@
                        error = EINTR; /* XXX ERESTART?  */
                        break;
                }
-
-               /* Transfer n bytes in and enter them into the pool.  */
-               error = uiomove(buf, n, uio);
-               if (error)
-                       break;
-               rnd_add_data(&user_rndsource, buf, n, privileged ? n*NBBY : 0);
-               any = true;
        }
 
        /* Zero the buffer and free it.  */