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    SubjectRe: [PATCH] ftrace: Disable function tracing during suspend/resume and hibernation, again
    Date
    On Monday, May 21, 2012, Srivatsa S. Bhat wrote:
    > 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

    Queued up for 3.6 in linux-pm/linux-next.

    Thanks,
    Rafael


    > ---
    >
    > kernel/power/hibernate.c | 6 ++++++
    > kernel/power/suspend.c | 3 +++
    > 2 files changed, 9 insertions(+), 0 deletions(-)
    >
    > diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
    > index e09dfbf..52a1817 100644
    > --- a/kernel/power/hibernate.c
    > +++ b/kernel/power/hibernate.c
    > @@ -352,6 +352,7 @@ int hibernation_snapshot(int platform_mode)
    > }
    >
    > suspend_console();
    > + ftrace_stop();
    > pm_restrict_gfp_mask();
    >
    > error = dpm_suspend(PMSG_FREEZE);
    > @@ -377,6 +378,7 @@ int hibernation_snapshot(int platform_mode)
    > if (error || !in_suspend)
    > pm_restore_gfp_mask();
    >
    > + ftrace_start();
    > resume_console();
    > dpm_complete(msg);
    >
    > @@ -479,6 +481,7 @@ 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) {
    > @@ -486,6 +489,7 @@ int hibernation_restore(int platform_mode)
    > dpm_resume_end(PMSG_RECOVER);
    > }
    > pm_restore_gfp_mask();
    > + ftrace_start();
    > resume_console();
    > pm_restore_console();
    > return error;
    > @@ -512,6 +516,7 @@ 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)
    > @@ -555,6 +560,7 @@ int hibernation_platform_enter(void)
    > Resume_devices:
    > entering_platform_hibernation = false;
    > dpm_resume_end(PMSG_RESTORE);
    > + ftrace_start();
    > resume_console();
    >
    > Close:
    > diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
    > index 396d262..c8b7446 100644
    > --- 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_state_t state)
    > 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_state_t state)
    > 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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