random: remove some prefetch logic (6d38b827) · Commits · 戴 / test

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:

Matt Mackall <mpm@selenic.com> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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 */

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