From c5c6ba4e08ab9c9e390a0f3a7d9a5c332f5cc6ef Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Mon, 25 Sep 2006 23:32:58 -0700 Subject: [PATCH] [PATCH] PM: Add pm_trace switch Add the pm_trace attribute in /sys/power which has to be explicitly set to one to really enable the "PM tracing" code compiled in when CONFIG_PM_TRACE is set (which modifies the machine's CMOS clock in unpredictable ways). Signed-off-by: Rafael J. Wysocki Acked-by: Pavel Machek Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/power/interface.txt | 15 +++++++++++++++ include/linux/resume-trace.h | 24 ++++++++++++++---------- kernel/power/main.c | 30 ++++++++++++++++++++++++++++++ 3 files changed, 59 insertions(+), 10 deletions(-) diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt index 4117802af0f8..a66bec222b16 100644 --- a/Documentation/power/interface.txt +++ b/Documentation/power/interface.txt @@ -52,3 +52,18 @@ suspend image will be as small as possible. Reading from this file will display the current image size limit, which is set to 500 MB by default. + +/sys/power/pm_trace controls the code which saves the last PM event point in +the RTC across reboots, so that you can debug a machine that just hangs +during suspend (or more commonly, during resume). Namely, the RTC is only +used to save the last PM event point if this file contains '1'. Initially it +contains '0' which may be changed to '1' by writing a string representing a +nonzero integer into it. + +To use this debugging feature you should attempt to suspend the machine, then +reboot it and run + + dmesg -s 1000000 | grep 'hash matches' + +CAUTION: Using it will cause your machine's real-time (CMOS) clock to be +set to a random invalid time after a resume. diff --git a/include/linux/resume-trace.h b/include/linux/resume-trace.h index a376bd4ade39..81e9299ca148 100644 --- a/include/linux/resume-trace.h +++ b/include/linux/resume-trace.h @@ -3,21 +3,25 @@ #ifdef CONFIG_PM_TRACE +extern int pm_trace_enabled; + struct device; extern void set_trace_device(struct device *); extern void generate_resume_trace(void *tracedata, unsigned int user); #define TRACE_DEVICE(dev) set_trace_device(dev) -#define TRACE_RESUME(user) do { \ - void *tracedata; \ - asm volatile("movl $1f,%0\n" \ - ".section .tracedata,\"a\"\n" \ - "1:\t.word %c1\n" \ - "\t.long %c2\n" \ - ".previous" \ - :"=r" (tracedata) \ - : "i" (__LINE__), "i" (__FILE__)); \ - generate_resume_trace(tracedata, user); \ +#define TRACE_RESUME(user) do { \ + if (pm_trace_enabled) { \ + void *tracedata; \ + asm volatile("movl $1f,%0\n" \ + ".section .tracedata,\"a\"\n" \ + "1:\t.word %c1\n" \ + "\t.long %c2\n" \ + ".previous" \ + :"=r" (tracedata) \ + : "i" (__LINE__), "i" (__FILE__)); \ + generate_resume_trace(tracedata, user); \ + } \ } while (0) #else diff --git a/kernel/power/main.c b/kernel/power/main.c index 4d403323a7bb..873228c71dab 100644 --- a/kernel/power/main.c +++ b/kernel/power/main.c @@ -17,6 +17,7 @@ #include #include #include +#include #include "power.h" @@ -281,10 +282,39 @@ static ssize_t state_store(struct subsystem * subsys, const char * buf, size_t n power_attr(state); +#ifdef CONFIG_PM_TRACE +int pm_trace_enabled; + +static ssize_t pm_trace_show(struct subsystem * subsys, char * buf) +{ + return sprintf(buf, "%d\n", pm_trace_enabled); +} + +static ssize_t +pm_trace_store(struct subsystem * subsys, const char * buf, size_t n) +{ + int val; + + if (sscanf(buf, "%d", &val) == 1) { + pm_trace_enabled = !!val; + return n; + } + return -EINVAL; +} + +power_attr(pm_trace); + +static struct attribute * g[] = { + &state_attr.attr, + &pm_trace_attr.attr, + NULL, +}; +#else static struct attribute * g[] = { &state_attr.attr, NULL, }; +#endif /* CONFIG_PM_TRACE */ static struct attribute_group attr_group = { .attrs = g, -- 2.30.2