Module Name: src
Committed By: riastradh
Date: Sun Mar 6 09:03:42 UTC 2022
Modified Files:
src/sys/dev/usb: usb.c
Log Message:
usb(4): Use atomics for usb_async_proc.
This is written under proc_lock and read without it in usb_add_event,
so using atomics pacifies the sanitizer. No memory ordering needed
because the value isn't actually used until the softint runs, using
it under proc_lock. Kind of a micro-optimization, but let's avoid
contention on proc_lock in the common case of no usb_async_proc set
up (why is this a system global, anyway? and why is there a softint
if usb_add_event always runs at IPL_NONE?).
Reported-by: [email protected]
To generate a diff of this commit:
cvs rdiff -u -r1.198 -r1.199 src/sys/dev/usb/usb.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/usb/usb.c
diff -u src/sys/dev/usb/usb.c:1.198 src/sys/dev/usb/usb.c:1.199
--- src/sys/dev/usb/usb.c:1.198 Sun Oct 10 20:14:09 2021
+++ src/sys/dev/usb/usb.c Sun Mar 6 09:03:42 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: usb.c,v 1.198 2021/10/10 20:14:09 jmcneill Exp $ */
+/* $NetBSD: usb.c,v 1.199 2022/03/06 09:03:42 riastradh Exp $ */
/*
* Copyright (c) 1998, 2002, 2008, 2012 The NetBSD Foundation, Inc.
@@ -37,7 +37,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: usb.c,v 1.198 2021/10/10 20:14:09 jmcneill Exp $");
+__KERNEL_RCSID(0, "$NetBSD: usb.c,v 1.199 2022/03/06 09:03:42 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "opt_usb.h"
@@ -833,7 +833,7 @@ usbopen(dev_t dev, int flag, int mode, s
return EBUSY;
usb_dev_open = 1;
mutex_enter(&proc_lock);
- usb_async_proc = NULL;
+ atomic_store_relaxed(&usb_async_proc, NULL);
mutex_exit(&proc_lock);
return 0;
}
@@ -913,7 +913,7 @@ usbclose(dev_t dev, int flag, int mode,
if (unit == USB_DEV_MINOR) {
mutex_enter(&proc_lock);
- usb_async_proc = NULL;
+ atomic_store_relaxed(&usb_async_proc, NULL);
mutex_exit(&proc_lock);
usb_dev_open = 0;
}
@@ -937,10 +937,8 @@ usbioctl(dev_t devt, u_long cmd, void *d
case FIOASYNC:
mutex_enter(&proc_lock);
- if (*(int *)data)
- usb_async_proc = l->l_proc;
- else
- usb_async_proc = NULL;
+ atomic_store_relaxed(&usb_async_proc,
+ *(int *)data ? l->l_proc : NULL);
mutex_exit(&proc_lock);
return 0;
@@ -1317,7 +1315,7 @@ usb_add_event(int type, struct usb_event
SIMPLEQ_INSERT_TAIL(&usb_events, ueq, next);
cv_signal(&usb_event_cv);
selnotify(&usb_selevent, 0, 0);
- if (usb_async_proc != NULL) {
+ if (atomic_load_relaxed(&usb_async_proc) != NULL) {
kpreempt_disable();
softint_schedule(usb_async_sih);
kpreempt_enable();
@@ -1331,7 +1329,7 @@ usb_async_intr(void *cookie)
proc_t *proc;
mutex_enter(&proc_lock);
- if ((proc = usb_async_proc) != NULL)
+ if ((proc = atomic_load_relaxed(&usb_async_proc)) != NULL)
psignal(proc, SIGIO);
mutex_exit(&proc_lock);
}
