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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>
This commit is contained in:
Matt Mackall 2008-04-29 01:03:07 -07:00 committed by Linus Torvalds
parent e68e5b664e
commit adc782dae6
1 changed files with 15 additions and 17 deletions
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32
drivers/char/random.c
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@ -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: