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Date:      Sat, 27 Oct 2018 21:04:34 +0000 (UTC)
From:      Vladimir Kondratyev <wulf@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r339824 - head/sys/dev/evdev
Message-ID:  <201810272104.w9RL4YIM043919@repo.freebsd.org>
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Author: wulf
Date: Sat Oct 27 21:04:34 2018
New Revision: 339824
URL: https://svnweb.freebsd.org/changeset/base/339824

Log:
  evdev: disable evdev if it is invoked from KDB or panic context
  
  This allow to prevent deadlock on entering KDB if one of evdev locks is
  already taken by userspace process.
  
  Also this change discards all but LED console events produced by KDB as
  unrelated to userspace.
  
  Tested by:	dumbbell (as part of D15070)
  Objected by:	bde (as 'KDB lock an already locked mutex' problem solution)
  MFC after:	1 month

Modified:
  head/sys/dev/evdev/cdev.c
  head/sys/dev/evdev/evdev.c
  head/sys/dev/evdev/evdev_private.h

Modified: head/sys/dev/evdev/cdev.c
==============================================================================
--- head/sys/dev/evdev/cdev.c	Sat Oct 27 20:22:41 2018	(r339823)
+++ head/sys/dev/evdev/cdev.c	Sat Oct 27 21:04:34 2018	(r339824)
@@ -349,6 +349,19 @@ evdev_ioctl(struct cdev *dev, u_long cmd, caddr_t data
 	if (client->ec_revoked || evdev == NULL)
 		return (ENODEV);
 
+	/*
+	 * Fix evdev state corrupted with discarding of kdb events.
+	 * EVIOCGKEY and EVIOCGLED ioctls can suffer from this.
+	 */
+	if (evdev->ev_kdb_active) {
+		EVDEV_LOCK(evdev);
+		if (evdev->ev_kdb_active) {
+			evdev->ev_kdb_active = false;
+			evdev_restore_after_kdb(evdev);
+		}
+		EVDEV_UNLOCK(evdev);
+	}
+
 	/* file I/O ioctl handling */
 	switch (cmd) {
 	case FIOSETOWN:

Modified: head/sys/dev/evdev/evdev.c
==============================================================================
--- head/sys/dev/evdev/evdev.c	Sat Oct 27 20:22:41 2018	(r339823)
+++ head/sys/dev/evdev/evdev.c	Sat Oct 27 21:04:34 2018	(r339824)
@@ -32,9 +32,11 @@
 #include <sys/param.h>
 #include <sys/bitstring.h>
 #include <sys/conf.h>
+#include <sys/kdb.h>
 #include <sys/kernel.h>
 #include <sys/malloc.h>
 #include <sys/module.h>
+#include <sys/proc.h>
 #include <sys/sysctl.h>
 #include <sys/systm.h>
 
@@ -763,6 +765,30 @@ evdev_send_event(struct evdev_dev *evdev, uint16_t typ
 	}
 }
 
+void
+evdev_restore_after_kdb(struct evdev_dev *evdev)
+{
+	int code;
+
+	EVDEV_LOCK_ASSERT(evdev);
+
+	/* Report postponed leds */
+	for (code = 0; code < LED_CNT; code++)
+		if (bit_test(evdev->ev_kdb_led_states, code))
+			evdev_send_event(evdev, EV_LED, code,
+			    !bit_test(evdev->ev_led_states, code));
+	bit_nclear(evdev->ev_kdb_led_states, 0, LED_MAX);
+
+	/* Release stuck keys (CTRL + ALT + ESC) */
+	evdev_stop_repeat(evdev);
+	for (code = 0; code < KEY_CNT; code++) {
+		if (bit_test(evdev->ev_key_states, code)) {
+			evdev_send_event(evdev, EV_KEY, code, KEY_EVENT_UP);
+			evdev_send_event(evdev, EV_SYN, SYN_REPORT, 1);
+		}
+	}
+}
+
 int
 evdev_push_event(struct evdev_dev *evdev, uint16_t type, uint16_t code,
     int32_t value)
@@ -771,7 +797,25 @@ evdev_push_event(struct evdev_dev *evdev, uint16_t typ
 	if (evdev_check_event(evdev, type, code, value) != 0)
 		return (EINVAL);
 
+	/*
+	 * Discard all but LEDs kdb events as unrelated to userspace.
+	 * Aggregate LED updates and postpone reporting until kdb deactivation.
+	 */
+	if (kdb_active || SCHEDULER_STOPPED()) {
+		evdev->ev_kdb_active = true;
+		if (type == EV_LED)
+			bit_set(evdev->ev_kdb_led_states,
+			    bit_test(evdev->ev_led_states, code) != value);
+		return (0);
+	}
+
 	EVDEV_ENTER(evdev);
+
+	/* Fix evdev state corrupted with discarding of kdb events */
+	if (evdev->ev_kdb_active) {
+		evdev->ev_kdb_active = false;
+		evdev_restore_after_kdb(evdev);
+	}
 
 	evdev_modify_event(evdev, type, code, &value);
 	if (type == EV_SYN && code == SYN_REPORT &&

Modified: head/sys/dev/evdev/evdev_private.h
==============================================================================
--- head/sys/dev/evdev/evdev_private.h	Sat Oct 27 20:22:41 2018	(r339823)
+++ head/sys/dev/evdev/evdev_private.h	Sat Oct 27 21:04:34 2018	(r339824)
@@ -117,6 +117,10 @@ struct evdev_dev
 	bitstr_t		bit_decl(ev_sw_states, SW_CNT);
 	bool			ev_report_opened;
 
+	/* KDB state: */
+	bool			ev_kdb_active;
+	bitstr_t		bit_decl(ev_kdb_led_states, LED_CNT);
+
 	/* Multitouch protocol type B state: */
 	struct evdev_mt *	ev_mt;
 
@@ -190,6 +194,7 @@ int evdev_cdev_destroy(struct evdev_dev *);
 bool evdev_event_supported(struct evdev_dev *, uint16_t);
 void evdev_set_abs_bit(struct evdev_dev *, uint16_t);
 void evdev_set_absinfo(struct evdev_dev *, uint16_t, struct input_absinfo *);
+void evdev_restore_after_kdb(struct evdev_dev *);
 
 /* Client interface: */
 int evdev_register_client(struct evdev_dev *, struct evdev_client *);

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