ftrace: Disable function tracing during suspend/resume and hibernation, again

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>
Cc: stable@vger.kernel.org
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 6 insertions, 0 deletions

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 21ad3fe3164f..0d4b354bc1be 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -358,6 +358,7 @@ int hibernation_snapshot(int platform_mode)
         }
 
         suspend_console();
+        ftrace_stop();
         pm_restrict_gfp_mask();
 
         error = dpm_suspend(PMSG_FREEZE);
@@ -383,6 +384,7 @@ int hibernation_snapshot(int platform_mode)
         if (error || !in_suspend)
                 pm_restore_gfp_mask();
 
+        ftrace_start();
         resume_console();
         dpm_complete(msg);
 
@@ -485,6 +487,7 @@ int hibernation_restore(int platform_mode)
 
         pm_prepare_console();
         suspend_console();
+        ftrace_stop();
         pm_restrict_gfp_mask();
         error = dpm_suspend_start(PMSG_QUIESCE);
         if (!error) {
@@ -492,6 +495,7 @@ int hibernation_restore(int platform_mode)
                 dpm_resume_end(PMSG_RECOVER);
         }
         pm_restore_gfp_mask();
+        ftrace_start();
         resume_console();
         pm_restore_console();
         return error;
@@ -518,6 +522,7 @@ 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)
@@ -561,6 +566,7 @@ int hibernation_platform_enter(void)
  Resume_devices:
         entering_platform_hibernation = false;
         dpm_resume_end(PMSG_RESTORE);
+        ftrace_start();
         resume_console();
 
  Close: