PM: Add sysfs attr for rechecking dev hash from PM trace

If the device which fails to resume is part of a loadable kernel module it won't be checked at startup against the magic number stored in the RTC. Add a read-only sysfs attribute /sys/power/pm_trace_dev_match which contains a list of newline separated devices (usually just the one) which currently match the last magic number. This allows the device which is failing to resume to be found after the modules are loaded again. Signed-off-by: James Hogan <james@albanarts.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

PM: Add sysfs attr for rechecking dev hash from PM trace
If the device which fails to resume is part of a loadable kernel module it won't be checked at startup against the magic number stored in the RTC. Add a read-only sysfs attribute /sys/power/pm_trace_dev_match which contains a list of newline separated devices (usually just the one) which currently match the last magic number. This allows the device which is failing to resume to be found after the modules are loaded again. Signed-off-by: James Hogan <james@albanarts.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
James Hogan · Rafael J. Wysocki
1 parent 2ac21c6bc4
Showing 5 changed files with 87 additions and 0 deletions Side-by-side Diff
Documentation/ABI/testing/sysfs-power
Documentation/power/s2ram.txt
drivers/base/power/trace.c
include/linux/resume-trace.h
kernel/power/main.c
@@ -99,8 +99,37 @@
  
 		dmesg -s 1000000 | grep 'hash matches'
  
+		If you do not get any matches (or they appear to be false
+		positives), it is possible that the last PM event point
+		referred to a device created by a loadable kernel module.  In
+		this case cat /sys/power/pm_trace_dev_match (see below) after
+		your system is started up and the kernel modules are loaded.
+
 		CAUTION: Using it will cause your machine's real-time (CMOS)
 		clock to be set to a random invalid time after a resume.
+
+What;		/sys/power/pm_trace_dev_match
+Date:		October 2010
+Contact:	James Hogan <james@albanarts.com>
+Description:
+		The /sys/power/pm_trace_dev_match file contains the name of the
+		device associated with the last PM event point saved in the RTC
+		across reboots when pm_trace has been used.  More precisely it
+		contains the list of current devices (including those
+		registered by loadable kernel modules since boot) which match
+		the device hash in the RTC at boot, with a newline after each
+		one.
+
+		The advantage of this file over the hash matches printed to the
+		kernel log (see /sys/power/pm_trace), is that it includes
+		devices created after boot by loadable kernel modules.
+
+		Due to the small hash size necessary to fit in the RTC, it is
+		possible that more than one device matches the hash, in which
+		case further investigation is required to determine which
+		device is causing the problem.  Note that genuine RTC clock
+		values (such as when pm_trace has not been used), can still
+		match a device and output it's name here.
  
 What:		/sys/power/pm_async
 Date:		January 2009
@@ -49,6 +49,13 @@
    device (lspci and /sys/devices/pci* is your friend), and see if you can
    fix it, disable it, or trace into its resume function.
  
+   If no device matches the hash (or any matches appear to be false positives),
+   the culprit may be a device from a loadable kernel module that is not loaded
+   until after the hash is checked. You can check the hash against the current
+   devices again after more modules are loaded using sysfs:
+
+	cat /sys/power/pm_trace_dev_match
+
 For example, the above happens to be the VGA device on my EVO, which I
 used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out
 that "radeonfb" simply cannot resume that device - it tries to set the
@@ -207,6 +207,37 @@
  
 static unsigned int hash_value_early_read;
  
+int show_trace_dev_match(char *buf, size_t size)
+{
+	unsigned int value = hash_value_early_read / (USERHASH * FILEHASH);
+	int ret = 0;
+	struct list_head *entry;
+
+	/*
+	 * It's possible that multiple devices will match the hash and we can't
+	 * tell which is the culprit, so it's best to output them all.
+	 */
+	device_pm_lock();
+	entry = dpm_list.prev;
+	while (size && entry != &dpm_list) {
+		struct device *dev = to_device(entry);
+		unsigned int hash = hash_string(DEVSEED, dev_name(dev),
+						DEVHASH);
+		if (hash == value) {
+			int len = snprintf(buf, size, "%s\n",
+					    dev_driver_string(dev));
+			if (len > size)
+				len = size;
+			buf += len;
+			ret += len;
+			size -= len;
+		}
+		entry = entry->prev;
+	}
+	device_pm_unlock();
+	return ret;
+}
+
 static int early_resume_init(void)
 {
 	hash_value_early_read = read_magic_time();
@@ -3,6 +3,7 @@
  
 #ifdef CONFIG_PM_TRACE
 #include <asm/resume-trace.h>
+#include <linux/types.h>
  
 extern int pm_trace_enabled;
  
@@ -14,6 +15,7 @@
 struct device;
 extern void set_trace_device(struct device *);
 extern void generate_resume_trace(const void *tracedata, unsigned int user);
+extern int show_trace_dev_match(char *buf, size_t size);
  
 #define TRACE_DEVICE(dev) do { \
 	if (pm_trace_enabled) \
@@ -281,12 +281,30 @@
 }
  
 power_attr(pm_trace);
+
+static ssize_t pm_trace_dev_match_show(struct kobject *kobj,
+				       struct kobj_attribute *attr,
+				       char *buf)
+{
+	return show_trace_dev_match(buf, PAGE_SIZE);
+}
+
+static ssize_t
+pm_trace_dev_match_store(struct kobject *kobj, struct kobj_attribute *attr,
+			 const char *buf, size_t n)
+{
+	return -EINVAL;
+}
+
+power_attr(pm_trace_dev_match);
+
 #endif /* CONFIG_PM_TRACE */
  
 static struct attribute * g[] = {
 	&state_attr.attr,
 #ifdef CONFIG_PM_TRACE
 	&pm_trace_attr.attr,
+	&pm_trace_dev_match_attr.attr,
 #endif
 #ifdef CONFIG_PM_SLEEP
 	&pm_async_attr.attr,
...	...	@@ -99,8 +99,37 @@
99	99
100	100	dmesg -s 1000000 \| grep 'hash matches'
101	101
	102	+ If you do not get any matches (or they appear to be false
	103	+ positives), it is possible that the last PM event point
	104	+ referred to a device created by a loadable kernel module. In
	105	+ this case cat /sys/power/pm_trace_dev_match (see below) after
	106	+ your system is started up and the kernel modules are loaded.
	107	+
102	108	CAUTION: Using it will cause your machine's real-time (CMOS)
103	109	clock to be set to a random invalid time after a resume.
	110	+
	111	+What; /sys/power/pm_trace_dev_match
	112	+Date: October 2010
	113	+Contact: James Hogan <james@albanarts.com>
	114	+Description:
	115	+ The /sys/power/pm_trace_dev_match file contains the name of the
	116	+ device associated with the last PM event point saved in the RTC
	117	+ across reboots when pm_trace has been used. More precisely it
	118	+ contains the list of current devices (including those
	119	+ registered by loadable kernel modules since boot) which match
	120	+ the device hash in the RTC at boot, with a newline after each
	121	+ one.
	122	+
	123	+ The advantage of this file over the hash matches printed to the
	124	+ kernel log (see /sys/power/pm_trace), is that it includes
	125	+ devices created after boot by loadable kernel modules.
	126	+
	127	+ Due to the small hash size necessary to fit in the RTC, it is
	128	+ possible that more than one device matches the hash, in which
	129	+ case further investigation is required to determine which
	130	+ device is causing the problem. Note that genuine RTC clock
	131	+ values (such as when pm_trace has not been used), can still
	132	+ match a device and output it's name here.
104	133
105	134	What: /sys/power/pm_async
106	135	Date: January 2009
...	...	@@ -49,6 +49,13 @@
49	49	device (lspci and /sys/devices/pci* is your friend), and see if you can
50	50	fix it, disable it, or trace into its resume function.
51	51
	52	+ If no device matches the hash (or any matches appear to be false positives),
	53	+ the culprit may be a device from a loadable kernel module that is not loaded
	54	+ until after the hash is checked. You can check the hash against the current
	55	+ devices again after more modules are loaded using sysfs:
	56	+
	57	+ cat /sys/power/pm_trace_dev_match
	58	+
52	59	For example, the above happens to be the VGA device on my EVO, which I
53	60	used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out
54	61	that "radeonfb" simply cannot resume that device - it tries to set the
...	...	@@ -207,6 +207,37 @@
207	207
208	208	static unsigned int hash_value_early_read;
209	209
	210	+int show_trace_dev_match(char *buf, size_t size)
	211	+{
	212	+ unsigned int value = hash_value_early_read / (USERHASH * FILEHASH);
	213	+ int ret = 0;
	214	+ struct list_head *entry;
	215	+
	216	+ /*
	217	+ * It's possible that multiple devices will match the hash and we can't
	218	+ * tell which is the culprit, so it's best to output them all.
	219	+ */
	220	+ device_pm_lock();
	221	+ entry = dpm_list.prev;
	222	+ while (size && entry != &dpm_list) {
	223	+ struct device *dev = to_device(entry);
	224	+ unsigned int hash = hash_string(DEVSEED, dev_name(dev),
	225	+ DEVHASH);
	226	+ if (hash == value) {
	227	+ int len = snprintf(buf, size, "%s\n",
	228	+ dev_driver_string(dev));
	229	+ if (len > size)
	230	+ len = size;
	231	+ buf += len;
	232	+ ret += len;
	233	+ size -= len;
	234	+ }
	235	+ entry = entry->prev;
	236	+ }
	237	+ device_pm_unlock();
	238	+ return ret;
	239	+}
	240	+
210	241	static int early_resume_init(void)
211	242	{
212	243	hash_value_early_read = read_magic_time();
...	...	@@ -3,6 +3,7 @@
3	3
4	4	#ifdef CONFIG_PM_TRACE
5	5	#include <asm/resume-trace.h>
	6	+#include <linux/types.h>
6	7
7	8	extern int pm_trace_enabled;
8	9
...	...	@@ -14,6 +15,7 @@
14	15	struct device;
15	16	extern void set_trace_device(struct device *);
16	17	extern void generate_resume_trace(const void *tracedata, unsigned int user);
	18	+extern int show_trace_dev_match(char *buf, size_t size);
17	19
18	20	#define TRACE_DEVICE(dev) do { \
19	21	if (pm_trace_enabled) \
...	...	@@ -281,12 +281,30 @@
281	281	}
282	282
283	283	power_attr(pm_trace);
	284	+
	285	+static ssize_t pm_trace_dev_match_show(struct kobject *kobj,
	286	+ struct kobj_attribute *attr,
	287	+ char *buf)
	288	+{
	289	+ return show_trace_dev_match(buf, PAGE_SIZE);
	290	+}
	291	+
	292	+static ssize_t
	293	+pm_trace_dev_match_store(struct kobject kobj, struct kobj_attribute attr,
	294	+ const char *buf, size_t n)
	295	+{
	296	+ return -EINVAL;
	297	+}
	298	+
	299	+power_attr(pm_trace_dev_match);
	300	+
284	301	#endif /* CONFIG_PM_TRACE */
285	302
286	303	static struct attribute * g[] = {
287	304	&state_attr.attr,
288	305	#ifdef CONFIG_PM_TRACE
289	306	&pm_trace_attr.attr,
	307	+ &pm_trace_dev_match_attr.attr,
290	308	#endif
291	309	#ifdef CONFIG_PM_SLEEP
292	310	&pm_async_attr.attr,