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uhid(4): Omit needless softint indirection. 

USB xfer callbacks already run in softint context at IPL_SOFTSERIAL,
and I see no reason why the call to psignal must happen instead at
the lower priority of IPL_SOFTCLOCK, so let's avoid using up the
scarce resource of softints for something that doesn't need 'em.

While here, use atomic_store_relaxed to update sc->sc_async and
atomic_load_relaxed to optimisitcally test it without acquiring
proc_lock.
This commit is contained in:
riastradh 2020-11-30 00:48:35 +00:00
parent 3766bfcd77
commit 92f37f2423
1 changed files with 15 additions and 26 deletions
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41
sys/dev/usb/uhid.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: uhid.c,v 1.115 2020/11/29 22:54:51 riastradh Exp $ */
/* $NetBSD: uhid.c,v 1.116 2020/11/30 00:48:35 riastradh Exp $ */
/*
* Copyright (c) 1998, 2004, 2008, 2012 The NetBSD Foundation, Inc.
@ -35,7 +35,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uhid.c,v 1.115 2020/11/29 22:54:51 riastradh Exp $");
__KERNEL_RCSID(0, "$NetBSD: uhid.c,v 1.116 2020/11/30 00:48:35 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "opt_compat_netbsd.h"
@ -138,7 +138,6 @@ const struct cdevsw uhid_cdevsw = {
};
Static void uhid_intr(struct uhidev *, void *, u_int);
Static void uhid_softintr(void *);
Static int uhid_do_read(struct uhid_softc *, struct uio *, int);
Static int uhid_do_write(struct uhid_softc *, struct uio *, int);
@ -180,7 +179,6 @@ uhid_attach(device_t parent, device_t self, void *aux)
sc->sc_hdev.sc_intr = uhid_intr;
sc->sc_hdev.sc_parent = uha->parent;
sc->sc_hdev.sc_report_id = uha->reportid;
sc->sc_sih = softint_establish(SOFTINT_CLOCK, uhid_softintr, sc);
uhidev_get_report_desc(uha->parent, &desc, &size);
repid = uha->reportid;
@ -277,7 +275,6 @@ uhid_detach(device_t self, int flags)
cv_destroy(&sc->sc_detach_cv);
mutex_destroy(&sc->sc_lock);
seldestroy(&sc->sc_rsel);
softint_disestablish(sc->sc_sih);
return 0;
}
@ -304,26 +301,18 @@ uhid_intr(struct uhidev *addr, void *data, u_int len)
DPRINTFN(5, ("uhid_intr: waking %p\n", &sc->sc_q));
cv_broadcast(&sc->sc_cv);
selnotify(&sc->sc_rsel, 0, NOTE_SUBMIT);
if (sc->sc_async != NULL) {
DPRINTFN(3, ("uhid_intr: sending SIGIO %p\n", sc->sc_async));
softint_schedule(sc->sc_sih);
if (atomic_load_relaxed(&sc->sc_async) != NULL) {
mutex_enter(&proc_lock);
if (sc->sc_async != NULL) {
DPRINTFN(3, ("uhid_intr: sending SIGIO to %jd\n",
(intmax_t)sc->sc_async->p_pid));
psignal(sc->sc_async, SIGIO);
}
mutex_exit(&proc_lock);
}
mutex_exit(&sc->sc_lock);
}
void
uhid_softintr(void *cookie)
{
struct uhid_softc *sc;
sc = cookie;
mutex_enter(&proc_lock);
if (sc->sc_async != NULL)
psignal(sc->sc_async, SIGIO);
mutex_exit(&proc_lock);
}
static int
uhidopen(dev_t dev, int flag, int mode, struct lwp *l)
{
@ -367,7 +356,7 @@ uhidopen(dev_t dev, int flag, int mode, struct lwp *l)
/* Paranoia: reset SIGIO before enabling interrputs. */
mutex_enter(&proc_lock);
sc->sc_async = NULL;
atomic_store_relaxed(&sc->sc_async, NULL);
mutex_exit(&proc_lock);
/* Open the uhidev -- after this point we can get interrupts. */
@ -390,7 +379,7 @@ fail2: __unused
uhidev_close(&sc->sc_hdev);
fail1: selnotify(&sc->sc_rsel, POLLHUP, 0);
mutex_enter(&proc_lock);
sc->sc_async = NULL;
atomic_store_relaxed(&sc->sc_async, NULL);
mutex_exit(&proc_lock);
if (sc->sc_osize > 0) {
kmem_free(sc->sc_obuf, sc->sc_osize);
@ -429,7 +418,7 @@ uhidclose(dev_t dev, int flag, int mode, struct lwp *l)
/* Reset SIGIO. */
mutex_enter(&proc_lock);
sc->sc_async = NULL;
atomic_store_relaxed(&sc->sc_async, NULL);
mutex_exit(&proc_lock);
/* Free the buffer and queue. */
@ -644,10 +633,10 @@ uhid_do_ioctl(struct uhid_softc *sc, u_long cmd, void *addr,
mutex_exit(&proc_lock);
return EBUSY;
}
sc->sc_async = l->l_proc;
atomic_store_relaxed(&sc->sc_async, l->l_proc);
DPRINTF(("uhid_do_ioctl: FIOASYNC %p\n", l->l_proc));
} else
sc->sc_async = NULL;
atomic_store_relaxed(&sc->sc_async, NULL);
mutex_exit(&proc_lock);
break;