Commit 2132a96f authored by Greg Price's avatar Greg Price Committed by Theodore Ts'o
Browse files

random: clarify bits/bytes in wakeup thresholds 



These are a recurring cause of confusion, so rename them to
hopefully be clearer.

Signed-off-by: default avatarGreg Price <price@mit.edu>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 7d1b08c4

drivers/char/random.c

+17 −17
Original line number Diff line number Diff line
@@ -295,14 +295,14 @@ 
 * The minimum number of bits of entropy before we wake up a read on

 * /dev/random.  Should be enough to do a significant reseed.

 */

static int random_read_wakeup_thresh = 64;

static int random_read_wakeup_bits = 64;



/*

 * If the entropy count falls under this number of bits, then we

 * should wake up processes which are selecting or polling on write

 * access to /dev/random.

 */

static int random_write_wakeup_thresh = 28 * OUTPUT_POOL_WORDS;

static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;



/*

 * The minimum number of seconds between urandom pool reseeding.  We
@@ -669,7 +669,7 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) 
		int entropy_bits = entropy_count >> ENTROPY_SHIFT;



		/* should we wake readers? */

		if (entropy_bits >= random_read_wakeup_thresh) {

		if (entropy_bits >= random_read_wakeup_bits) {

			wake_up_interruptible(&random_read_wait);

			kill_fasync(&fasync, SIGIO, POLL_IN);

		}
@@ -678,9 +678,9 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) 
		 * forth between them, until the output pools are 75%

		 * full.

		 */

		if (entropy_bits > random_write_wakeup_thresh &&

		if (entropy_bits > random_write_wakeup_bits &&

		    r->initialized &&

		    r->entropy_total >= 2*random_read_wakeup_thresh) {

		    r->entropy_total >= 2*random_read_wakeup_bits) {

			static struct entropy_store *last = &blocking_pool;

			struct entropy_store *other = &blocking_pool;
@@ -924,19 +924,19 @@ static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes) 
{

	__u32	tmp[OUTPUT_POOL_WORDS];



	/* For /dev/random's pool, always leave two wakeup worth's BITS */

	int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;

	/* For /dev/random's pool, always leave two wakeups' worth */

	int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;

	int bytes = nbytes;



	/* pull at least as many as BYTES as wakeup BITS */

	bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);

	/* pull at least as much as a wakeup */

	bytes = max_t(int, bytes, random_read_wakeup_bits / 8);

	/* but never more than the buffer size */

	bytes = min_t(int, bytes, sizeof(tmp));



	trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,

				  ENTROPY_BITS(r), ENTROPY_BITS(r->pull));

	bytes = extract_entropy(r->pull, tmp, bytes,

				random_read_wakeup_thresh / 8, rsvd);

				random_read_wakeup_bits / 8, rsvd_bytes);

	mix_pool_bytes(r, tmp, bytes, NULL);

	credit_entropy_bits(r, bytes*8);

}
@@ -952,7 +952,7 @@ static void push_to_pool(struct work_struct *work) 
	struct entropy_store *r = container_of(work, struct entropy_store,

					      push_work);

	BUG_ON(!r);

	_xfer_secondary_pool(r, random_read_wakeup_thresh/8);

	_xfer_secondary_pool(r, random_read_wakeup_bits/8);

	trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,

			   r->pull->entropy_count >> ENTROPY_SHIFT);

}
@@ -987,7 +987,7 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min, 


	trace_debit_entropy(r->name, 8 * ibytes);

	if (ibytes &&

	    (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_thresh) {

	    (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {

		wake_up_interruptible(&random_write_wait);

		kill_fasync(&fasync, SIGIO, POLL_OUT);

	}
@@ -1303,7 +1303,7 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) 


		wait_event_interruptible(random_read_wait,

			ENTROPY_BITS(&input_pool) >=

			random_read_wakeup_thresh);

			random_read_wakeup_bits);

		if (signal_pending(current))

			return -ERESTARTSYS;

	}
@@ -1334,9 +1334,9 @@ random_poll(struct file *file, poll_table * wait) 
	poll_wait(file, &random_read_wait, wait);

	poll_wait(file, &random_write_wait, wait);

	mask = 0;

	if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_thresh)

	if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)

		mask |= POLLIN | POLLRDNORM;

	if (ENTROPY_BITS(&input_pool) < random_write_wakeup_thresh)

	if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)

		mask |= POLLOUT | POLLWRNORM;

	return mask;

}
@@ -1559,7 +1559,7 @@ struct ctl_table random_table[] = { 
	},

	{

		.procname	= "read_wakeup_threshold",

		.data		= &random_read_wakeup_thresh,

		.data		= &random_read_wakeup_bits,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,
@@ -1568,7 +1568,7 @@ struct ctl_table random_table[] = { 
	},

	{

		.procname	= "write_wakeup_threshold",

		.data		= &random_write_wakeup_thresh,

		.data		= &random_write_wakeup_bits,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,