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Subject[ 041/122] ftrace: Disable function tracing during suspend/resume and hibernation, again
Date
From: Greg KH <gregkh@linuxfoundation.org>

3.5-stable review patch. If anyone has any objections, please let me know.

------------------
From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>

commit 443772d408a25af62498793f6f805ce3c559309a upstream.

If function tracing is enabled for some of the low-level suspend/resume
functions, it leads to triple fault during resume from suspend, ultimately
ending up in a reboot instead of a resume (or a total refusal to come out
of suspended state, on some machines).

This issue was explained in more detail in commit f42ac38c59e0a03d (ftrace:
disable tracing for suspend to ram). However, the changes made by that commit
got reverted by commit cbe2f5a6e84eebb (tracing: allow tracing of
suspend/resume & hibernation code again). So, unfortunately since things are
not yet robust enough to allow tracing of low-level suspend/resume functions,
suspend/resume is still broken when ftrace is enabled.

So fix this by disabling function tracing during suspend/resume & hibernation.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/power/hibernate.c | 6 ++++++
kernel/power/suspend.c | 3 +++
2 files changed, 9 insertions(+)
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -353,6 +353,7 @@ int hibernation_snapshot(int platform_mo
}

suspend_console();
+ ftrace_stop();
pm_restrict_gfp_mask();

error = dpm_suspend(PMSG_FREEZE);
@@ -378,6 +379,7 @@ int hibernation_snapshot(int platform_mo
if (error || !in_suspend)
pm_restore_gfp_mask();

+ ftrace_start();
resume_console();
dpm_complete(msg);

@@ -480,6 +482,7 @@ int hibernation_restore(int platform_mod

pm_prepare_console();
suspend_console();
+ ftrace_stop();
pm_restrict_gfp_mask();
error = dpm_suspend_start(PMSG_QUIESCE);
if (!error) {
@@ -487,6 +490,7 @@ int hibernation_restore(int platform_mod
dpm_resume_end(PMSG_RECOVER);
}
pm_restore_gfp_mask();
+ ftrace_start();
resume_console();
pm_restore_console();
return error;
@@ -513,6 +517,7 @@ int hibernation_platform_enter(void)

entering_platform_hibernation = true;
suspend_console();
+ ftrace_stop();
error = dpm_suspend_start(PMSG_HIBERNATE);
if (error) {
if (hibernation_ops->recover)
@@ -556,6 +561,7 @@ int hibernation_platform_enter(void)
Resume_devices:
entering_platform_hibernation = false;
dpm_resume_end(PMSG_RESTORE);
+ ftrace_start();
resume_console();

Close:
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -24,6 +24,7 @@
#include <linux/export.h>
#include <linux/suspend.h>
#include <linux/syscore_ops.h>
+#include <linux/ftrace.h>
#include <trace/events/power.h>

#include "power.h"
@@ -212,6 +213,7 @@ int suspend_devices_and_enter(suspend_st
goto Close;
}
suspend_console();
+ ftrace_stop();
suspend_test_start();
error = dpm_suspend_start(PMSG_SUSPEND);
if (error) {
@@ -231,6 +233,7 @@ int suspend_devices_and_enter(suspend_st
suspend_test_start();
dpm_resume_end(PMSG_RESUME);
suspend_test_finish("resume devices");
+ ftrace_start();
resume_console();
Close:
if (suspend_ops->end)



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