[PATCH 36/36] random: convert to ->poll_mask

Christoph Hellwig
2018-01-17T19:29:57Z

The big change is that random_read_wait and random_write_wait are merged
into a single waitqueue that uses keyed wakeups. Because wait_event_*
doesn't know about that this will lead to occassional spurious wakeups
in _random_read and add_hwgenerator_randomness, but wait_event_* is
designed to handle these and were are not in a a hot path there.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/char/random.c | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 64b59562c872..9a1b85928de3 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -401,8 +401,7 @@ static struct poolinfo {
/*
* Static global variables
*/
-static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
-static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
+static DECLARE_WAIT_QUEUE_HEAD(random_wait);
static struct fasync_struct *fasync;

static DEFINE_SPINLOCK(random_ready_list_lock);
@@ -710,7 +709,7 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits)

/* should we wake readers? */
if (entropy_bits >= random_read_wakeup_bits) {
- wake_up_interruptible(&random_read_wait);
+ wake_up_interruptible_poll(&random_wait, POLLIN);
kill_fasync(&fasync, SIGIO, POLL_IN);
}
/* If the input pool is getting full, send some
@@ -1293,7 +1292,7 @@ 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_bits) {
- wake_up_interruptible(&random_write_wait);
+ wake_up_interruptible_poll(&random_wait, POLLOUT);
kill_fasync(&fasync, SIGIO, POLL_OUT);
}

@@ -1748,7 +1747,7 @@ _random_read(int nonblock, char __user *buf, size_t nbytes)
if (nonblock)
return -EAGAIN;

- wait_event_interruptible(random_read_wait,
+ wait_event_interruptible(random_wait,
ENTROPY_BITS(&input_pool) >=
random_read_wakeup_bits);
if (signal_pending(current))
@@ -1784,14 +1783,17 @@ urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
return ret;
}

+static struct wait_queue_head *
+random_get_poll_head(struct file *file, __poll_t events)
+{
+ return &random_wait;
+}
+
static __poll_t
-random_poll(struct file *file, poll_table * wait)
+random_poll_mask(struct file *file, __poll_t events)
{
- __poll_t mask;
+ __poll_t mask = 0;

- poll_wait(file, &random_read_wait, wait);
- poll_wait(file, &random_write_wait, wait);
- mask = 0;
if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
mask |= POLLIN | POLLRDNORM;
if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
@@ -1890,7 +1892,8 @@ static int random_fasync(int fd, struct file *filp, int on)
const struct file_operations random_fops = {
.read = random_read,
.write = random_write,
- .poll = random_poll,
+ .get_poll_head = random_get_poll_head,
+ .poll_mask = random_poll_mask,
.unlocked_ioctl = random_ioctl,
.fasync = random_fasync,
.llseek = noop_llseek,
@@ -2223,7 +2226,7 @@ void add_hwgenerator_randomness(const char *buffer, size_t count,
* We'll be woken up again once below random_write_wakeup_thresh,
* or when the calling thread is about to terminate.
*/
- wait_event_interruptible(random_write_wait, kthread_should_stop() ||
+ wait_event_interruptible(random_wait, kthread_should_stop() ||
ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
mix_pool_bytes(poolp, buffer, count);
credit_entropy_bits(poolp, entropy);
--
2.14.2