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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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