From: Matt Mackall 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 Cc: Theodore Ts'o Signed-off-by: Andrew Morton --- drivers/char/random.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff -puN drivers/char/random.c~random-remove-some-prefetch-logic drivers/char/random.c --- a/drivers/char/random.c~random-remove-some-prefetch-logic +++ a/drivers/char/random.c @@ -457,7 +457,7 @@ static void __add_entropy_words(struct e 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 e 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 */ _