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Commit 6d38b827 authored by Matt Mackall's avatar Matt Mackall Committed by Linus Torvalds
Browse files

random: remove some prefetch logic 



The urandom output pool (ie the fast path) fits in one cacheline, so
this is pretty unnecessary. Further, the output path has already
fetched the entire pool to hash it before calling in here.

(This was the only user of prefetch_range in the kernel, and it passed
in words rather than bytes!)

Signed-off-by: default avatarMatt Mackall <mpm@selenic.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent feee7697

drivers/char/random.c

+2 −6
Original line number Diff line number Diff line
@@ -457,7 +457,7 @@ static void __add_entropy_words(struct entropy_store *r, const __u32 *in, 
	unsigned long i, add_ptr, tap1, tap2, tap3, tap4, tap5;

	int input_rotate;

	int wordmask = r->poolinfo->poolwords - 1;

	__u32 w, next_w;

	__u32 w;

	unsigned long flags;



	/* Taps are constant, so we can load them without holding r->lock.  */
@@ -466,17 +466,13 @@ static void __add_entropy_words(struct entropy_store *r, const __u32 *in, 
	tap3 = r->poolinfo->tap3;

	tap4 = r->poolinfo->tap4;

	tap5 = r->poolinfo->tap5;

	next_w = *in++;



	spin_lock_irqsave(&r->lock, flags);

	prefetch_range(r->pool, wordmask);

	input_rotate = r->input_rotate;

	add_ptr = r->add_ptr;



	while (nwords--) {

		w = rol32(next_w, input_rotate & 31);

		if (nwords > 0)

			next_w = *in++;

		w = rol32(*in++, input_rotate & 31);

		i = add_ptr = (add_ptr - 1) & wordmask;



		/* XOR in the various taps */