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authorMatt Mackall <mpm@selenic.com>2008-04-29 12:03:07 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-29 19:06:25 +0400
commitadc782dae6c4c0f6fb679a48a544cfbcd79ae3dc (patch)
tree67ad14a2905ff12603dd72601c3ee5398f7148fb /drivers/char/random.c
parente68e5b664ecb9bccf68102557107a6b6d739a97c (diff)
downloadlinux-adc782dae6c4c0f6fb679a48a544cfbcd79ae3dc.tar.xz
random: simplify and rename credit_entropy_store
- emphasize bits in the name - make zero bits lock-free - simplify logic 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>
Diffstat (limited to 'drivers/char/random.c')
-rw-r--r--drivers/char/random.c32
1 files changed, 15 insertions, 17 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index d33f52cd437b..2faeef28c209 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -441,7 +441,7 @@ static struct entropy_store nonblocking_pool = {
/*
* This function adds bytes into the entropy "pool". It does not
* update the entropy estimate. The caller should call
- * credit_entropy_store if this is appropriate.
+ * credit_entropy_bits if this is appropriate.
*
* The pool is stirred with a primitive polynomial of the appropriate
* degree, and then twisted. We twist by three bits at a time because
@@ -515,24 +515,22 @@ static void mix_pool_bytes(struct entropy_store *r, const void *in, int bytes)
/*
* Credit (or debit) the entropy store with n bits of entropy
*/
-static void credit_entropy_store(struct entropy_store *r, int nbits)
+static void credit_entropy_bits(struct entropy_store *r, int nbits)
{
unsigned long flags;
+ if (!nbits)
+ return;
+
spin_lock_irqsave(&r->lock, flags);
- if (r->entropy_count + nbits < 0) {
- DEBUG_ENT("negative entropy/overflow (%d+%d)\n",
- r->entropy_count, nbits);
+ DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
+ r->entropy_count += nbits;
+ if (r->entropy_count < 0) {
+ DEBUG_ENT("negative entropy/overflow\n");
r->entropy_count = 0;
- } else if (r->entropy_count + nbits > r->poolinfo->POOLBITS) {
+ } else if (r->entropy_count > r->poolinfo->POOLBITS)
r->entropy_count = r->poolinfo->POOLBITS;
- } else {
- r->entropy_count += nbits;
- if (nbits)
- DEBUG_ENT("added %d entropy credits to %s\n",
- nbits, r->name);
- }
/* should we wake readers? */
if (r == &input_pool && r->entropy_count >= random_read_wakeup_thresh)
@@ -619,8 +617,8 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
* Round down by 1 bit on general principles,
* and limit entropy entimate to 12 bits.
*/
- credit_entropy_store(&input_pool,
- min_t(int, fls(delta>>1), 11));
+ credit_entropy_bits(&input_pool,
+ min_t(int, fls(delta>>1), 11));
}
out:
preempt_enable();
@@ -702,7 +700,7 @@ static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
bytes = extract_entropy(r->pull, tmp, bytes,
random_read_wakeup_thresh / 8, rsvd);
mix_pool_bytes(r, tmp, bytes);
- credit_entropy_store(r, bytes*8);
+ credit_entropy_bits(r, bytes*8);
}
}
@@ -1073,7 +1071,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
return -EPERM;
if (get_user(ent_count, p))
return -EFAULT;
- credit_entropy_store(&input_pool, ent_count);
+ credit_entropy_bits(&input_pool, ent_count);
return 0;
case RNDADDENTROPY:
if (!capable(CAP_SYS_ADMIN))
@@ -1088,7 +1086,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
size);
if (retval < 0)
return retval;
- credit_entropy_store(&input_pool, ent_count);
+ credit_entropy_bits(&input_pool, ent_count);
return 0;
case RNDZAPENTCNT:
case RNDCLEARPOOL: