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authorLinus Torvalds <torvalds@linux-foundation.org>2018-06-28 09:43:44 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-28 10:40:47 -0700
commita11e1d432b51f63ba698d044441284a661f01144 (patch)
tree9f3c5a10bf0d7f9a342d5fb39c0c35ea14170124 /drivers/char
parentf57494321cbf5b1e7769b6135407d2995a369e28 (diff)
Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL
The poll() changes were not well thought out, and completely unexplained. They also caused a huge performance regression, because "->poll()" was no longer a trivial file operation that just called down to the underlying file operations, but instead did at least two indirect calls. Indirect calls are sadly slow now with the Spectre mitigation, but the performance problem could at least be largely mitigated by changing the "->get_poll_head()" operation to just have a per-file-descriptor pointer to the poll head instead. That gets rid of one of the new indirections. But that doesn't fix the new complexity that is completely unwarranted for the regular case. The (undocumented) reason for the poll() changes was some alleged AIO poll race fixing, but we don't make the common case slower and more complex for some uncommon special case, so this all really needs way more explanations and most likely a fundamental redesign. [ This revert is a revert of about 30 different commits, not reverted individually because that would just be unnecessarily messy - Linus ] Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/random.c29
1 files changed, 13 insertions, 16 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index a8fb0020ba5c..cd888d4ee605 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -402,7 +402,8 @@ static struct poolinfo {
/*
* Static global variables
*/
-static DECLARE_WAIT_QUEUE_HEAD(random_wait);
+static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
+static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
static struct fasync_struct *fasync;
static DEFINE_SPINLOCK(random_ready_list_lock);
@@ -721,8 +722,8 @@ retry:
/* should we wake readers? */
if (entropy_bits >= random_read_wakeup_bits &&
- wq_has_sleeper(&random_wait)) {
- wake_up_interruptible_poll(&random_wait, POLLIN);
+ wq_has_sleeper(&random_read_wait)) {
+ wake_up_interruptible(&random_read_wait);
kill_fasync(&fasync, SIGIO, POLL_IN);
}
/* If the input pool is getting full, send some
@@ -1396,7 +1397,7 @@ retry:
trace_debit_entropy(r->name, 8 * ibytes);
if (ibytes &&
(r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
- wake_up_interruptible_poll(&random_wait, POLLOUT);
+ wake_up_interruptible(&random_write_wait);
kill_fasync(&fasync, SIGIO, POLL_OUT);
}
@@ -1838,7 +1839,7 @@ _random_read(int nonblock, char __user *buf, size_t nbytes)
if (nonblock)
return -EAGAIN;
- wait_event_interruptible(random_wait,
+ wait_event_interruptible(random_read_wait,
ENTROPY_BITS(&input_pool) >=
random_read_wakeup_bits);
if (signal_pending(current))
@@ -1875,17 +1876,14 @@ 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_mask(struct file *file, __poll_t events)
+random_poll(struct file *file, poll_table * wait)
{
- __poll_t mask = 0;
+ __poll_t mask;
+ 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 |= EPOLLIN | EPOLLRDNORM;
if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
@@ -1992,8 +1990,7 @@ static int random_fasync(int fd, struct file *filp, int on)
const struct file_operations random_fops = {
.read = random_read,
.write = random_write,
- .get_poll_head = random_get_poll_head,
- .poll_mask = random_poll_mask,
+ .poll = random_poll,
.unlocked_ioctl = random_ioctl,
.fasync = random_fasync,
.llseek = noop_llseek,
@@ -2326,7 +2323,7 @@ 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_wait, kthread_should_stop() ||
+ wait_event_interruptible(random_write_wait, kthread_should_stop() ||
ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
mix_pool_bytes(poolp, buffer, count);
credit_entropy_bits(poolp, entropy);