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linux: fix ioctl performance for termios

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TCGETS et al are frequently issued by Linux binaries while the previous code
avoidably ping-pongs a global sx lock and serializes on Giant.

Note that even with the fix the common case will serialize on a per-tty lock.
This commit is contained in:
Mateusz Guzik 2020-07-04 06:25:41 +00:00
parent dc3c991598
commit d6d9ddd41f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=362922
1 changed files with 39 additions and 5 deletions
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44
sys/compat/linux/linux_ioctl.c
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@ -132,8 +132,6 @@ static struct linux_ioctl_handler socket_handler =
{ linux_ioctl_socket, LINUX_IOCTL_SOCKET_MIN, LINUX_IOCTL_SOCKET_MAX };
static struct linux_ioctl_handler sound_handler =
{ linux_ioctl_sound, LINUX_IOCTL_SOUND_MIN, LINUX_IOCTL_SOUND_MAX };
static struct linux_ioctl_handler termio_handler =
{ linux_ioctl_termio, LINUX_IOCTL_TERMIO_MIN, LINUX_IOCTL_TERMIO_MAX };
static struct linux_ioctl_handler private_handler =
{ linux_ioctl_private, LINUX_IOCTL_PRIVATE_MIN, LINUX_IOCTL_PRIVATE_MAX };
static struct linux_ioctl_handler drm_handler =
@ -156,7 +154,6 @@ DATA_SET(linux_ioctl_handler_set, hdio_handler);
DATA_SET(linux_ioctl_handler_set, disk_handler);
DATA_SET(linux_ioctl_handler_set, socket_handler);
DATA_SET(linux_ioctl_handler_set, sound_handler);
DATA_SET(linux_ioctl_handler_set, termio_handler);
DATA_SET(linux_ioctl_handler_set, private_handler);
DATA_SET(linux_ioctl_handler_set, drm_handler);
DATA_SET(linux_ioctl_handler_set, sg_handler);
@ -165,6 +162,14 @@ DATA_SET(linux_ioctl_handler_set, video2_handler);
DATA_SET(linux_ioctl_handler_set, fbsd_usb);
DATA_SET(linux_ioctl_handler_set, evdev_handler);
/*
* Keep sorted by low.
*/
static struct linux_ioctl_handler linux_ioctls[] = {
{ .func = linux_ioctl_termio, .low = LINUX_IOCTL_TERMIO_MIN,
.high = LINUX_IOCTL_TERMIO_MAX },
};
#ifdef __i386__
static TAILQ_HEAD(, linux_ioctl_handler_element) linux_ioctl_handlers =
TAILQ_HEAD_INITIALIZER(linux_ioctl_handlers);
@ -3558,8 +3563,8 @@ linux_ioctl_evdev(struct thread *td, struct linux_ioctl_args *args)
* main ioctl syscall function
*/
int
linux_ioctl(struct thread *td, struct linux_ioctl_args *args)
static int
linux_ioctl_fallback(struct thread *td, struct linux_ioctl_args *args)
{
struct file *fp;
struct linux_ioctl_handler_element *he;
@ -3620,6 +3625,35 @@ linux_ioctl(struct thread *td, struct linux_ioctl_args *args)
return (EINVAL);
}
int
linux_ioctl(struct thread *td, struct linux_ioctl_args *args)
{
struct linux_ioctl_handler *handler;
int error, cmd, i;
cmd = args->cmd & 0xffff;
/*
* array of ioctls known at compilation time. Elides a lot of work on
* each call compared to the list variant. Everything frequently used
* should be moved here.
*
* Arguably the magic creating the list should create an array instead.
*
* For now just a linear scan.
*/
for (i = 0; i < nitems(linux_ioctls); i++) {
handler = &linux_ioctls[i];
if (cmd >= handler->low && cmd <= handler->high) {
error = (*handler->func)(td, args);
if (error != ENOIOCTL) {
return (error);
}
}
}
return (linux_ioctl_fallback(td, args));
}
int
linux_ioctl_register_handler(struct linux_ioctl_handler *h)
{