106 lines
2.8 KiB
Diff
106 lines
2.8 KiB
Diff
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From 3d92c251c04b1b4c6363018220af42ec3a294d1e Mon Sep 17 00:00:00 2001
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From: Kenny Levinsen <kl@kl.wtf>
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Date: Sun, 27 Dec 2020 14:43:13 +0000
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Subject: ZEN: Input: evdev - use call_rcu when detaching client
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Significant time was spent on synchronize_rcu in evdev_detach_client
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when applications closed evdev devices. Switching VT away from a
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graphical environment commonly leads to mass input device closures,
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which could lead to noticable delays on systems with many input devices.
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Replace synchronize_rcu with call_rcu, deferring reclaim of the evdev
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client struct till after the RCU grace period instead of blocking the
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calling application.
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While this does not solve all slow evdev fd closures, it takes care of a
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good portion of them, including this simple test:
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#include <fcntl.h>
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#include <unistd.h>
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int main(int argc, char *argv[])
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{
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int idx, fd;
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const char *path = "/dev/input/event0";
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for (idx = 0; idx < 1000; idx++) {
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if ((fd = open(path, O_RDWR)) == -1) {
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return -1;
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}
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close(fd);
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}
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return 0;
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}
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Time to completion of above test when run locally:
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Before: 0m27.111s
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After: 0m0.018s
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Signed-off-by: Kenny Levinsen <kl@kl.wtf>
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---
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drivers/input/evdev.c | 19 +++++++++++--------
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1 file changed, 11 insertions(+), 8 deletions(-)
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--- a/drivers/input/evdev.c
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+++ b/drivers/input/evdev.c
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@@ -46,6 +46,7 @@ struct evdev_client {
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struct fasync_struct *fasync;
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struct evdev *evdev;
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struct list_head node;
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+ struct rcu_head rcu;
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enum input_clock_type clk_type;
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bool revoked;
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unsigned long *evmasks[EV_CNT];
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@@ -368,13 +369,22 @@ static void evdev_attach_client(struct e
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spin_unlock(&evdev->client_lock);
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}
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+static void evdev_reclaim_client(struct rcu_head *rp)
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+{
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+ struct evdev_client *client = container_of(rp, struct evdev_client, rcu);
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+ unsigned int i;
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+ for (i = 0; i < EV_CNT; ++i)
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+ bitmap_free(client->evmasks[i]);
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+ kvfree(client);
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+}
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+
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static void evdev_detach_client(struct evdev *evdev,
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struct evdev_client *client)
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{
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spin_lock(&evdev->client_lock);
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list_del_rcu(&client->node);
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spin_unlock(&evdev->client_lock);
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- synchronize_rcu();
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+ call_rcu(&client->rcu, evdev_reclaim_client);
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}
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static int evdev_open_device(struct evdev *evdev)
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@@ -427,7 +437,6 @@ static int evdev_release(struct inode *i
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{
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struct evdev_client *client = file->private_data;
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struct evdev *evdev = client->evdev;
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- unsigned int i;
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mutex_lock(&evdev->mutex);
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@@ -439,11 +448,6 @@ static int evdev_release(struct inode *i
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evdev_detach_client(evdev, client);
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- for (i = 0; i < EV_CNT; ++i)
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- bitmap_free(client->evmasks[i]);
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-
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- kvfree(client);
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-
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evdev_close_device(evdev);
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return 0;
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@@ -486,7 +490,6 @@ static int evdev_open(struct inode *inod
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err_free_client:
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evdev_detach_client(evdev, client);
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- kvfree(client);
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return error;
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}
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