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    Subject[PATCHv2 2/3] debugobjects: Extend to assert that an object is initialized
    Date
    From: Christine Chan <cschan@codeaurora.org>

    Calling del_timer_sync() on an uninitialized timer leads to a
    never ending loop in lock_timer_base() that spins checking for a
    non-NULL timer base. Add an assertion to debugobjects to catch
    usage of uninitialized objects so that we can initialize timers
    in the del_timer_sync() path before it calls lock_timer_base().

    Signed-off-by: Christine Chan <cschan@codeaurora.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: John Stultz <john.stultz@linaro.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    [sboyd: Clarify commit message]
    Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
    ---
    Documentation/DocBook/debugobjects.tmpl | 50 +++++++++++++++++++++++++++++++
    include/linux/debugobjects.h | 6 ++++
    lib/debugobjects.c | 38 +++++++++++++++++++++++
    3 files changed, 94 insertions(+), 0 deletions(-)

    diff --git a/Documentation/DocBook/debugobjects.tmpl b/Documentation/DocBook/debugobjects.tmpl
    index 08ff908..24979f6 100644
    --- a/Documentation/DocBook/debugobjects.tmpl
    +++ b/Documentation/DocBook/debugobjects.tmpl
    @@ -96,6 +96,7 @@
    <listitem><para>debug_object_deactivate</para></listitem>
    <listitem><para>debug_object_destroy</para></listitem>
    <listitem><para>debug_object_free</para></listitem>
    + <listitem><para>debug_object_assert_init</para></listitem>
    </itemizedlist>
    Each of these functions takes the address of the real object and
    a pointer to the object type specific debug description
    @@ -273,6 +274,26 @@
    debug checks.
    </para>
    </sect1>
    +
    + <sect1 id="debug_object_assert_init">
    + <title>debug_object_assert_init</title>
    + <para>
    + This function is called to assert that an object has been
    + initialized.
    + </para>
    + <para>
    + When the real object is not tracked by debugobjects, it calls
    + fixup_assert_init of the object type description structure
    + provided by the caller, with the hardcoded object state
    + ODEBUG_NOT_AVAILABLE. The fixup function can correct the problem
    + by calling debug_object_init and other specific initializing
    + functions.
    + </para>
    + <para>
    + When the real object is already tracked by debugobjects it is
    + ignored.
    + </para>
    + </sect1>
    </chapter>
    <chapter id="fixupfunctions">
    <title>Fixup functions</title>
    @@ -381,6 +402,35 @@
    statistics.
    </para>
    </sect1>
    + <sect1 id="fixup_assert_init">
    + <title>fixup_assert_init</title>
    + <para>
    + This function is called from the debug code whenever a problem
    + in debug_object_assert_init is detected.
    + </para>
    + <para>
    + Called from debug_object_assert_init() with a hardcoded state
    + ODEBUG_STATE_NOTAVAILABLE when the object is not found in the
    + debug bucket.
    + </para>
    + <para>
    + The function returns 1 when the fixup was successful,
    + otherwise 0. The return value is used to update the
    + statistics.
    + </para>
    + <para>
    + Note, this function should make sure debug_object_init() is
    + called before returning.
    + </para>
    + <para>
    + The handling of statically initialized objects is a special
    + case. The fixup function should check if this is a legitimate
    + case of a statically initialized object or not. In this case only
    + debug_object_init() should be called to make the object known to
    + the tracker. Then the function should return 0 because this is not
    + a real fixup.
    + </para>
    + </sect1>
    </chapter>
    <chapter id="bugs">
    <title>Known Bugs And Assumptions</title>
    diff --git a/include/linux/debugobjects.h b/include/linux/debugobjects.h
    index 65970b8..0e5f578 100644
    --- a/include/linux/debugobjects.h
    +++ b/include/linux/debugobjects.h
    @@ -46,6 +46,8 @@ struct debug_obj {
    * fails
    * @fixup_free: fixup function, which is called when the free check
    * fails
    + * @fixup_assert_init: fixup function, which is called when the assert_init
    + * check fails
    */
    struct debug_obj_descr {
    const char *name;
    @@ -54,6 +56,7 @@ struct debug_obj_descr {
    int (*fixup_activate) (void *addr, enum debug_obj_state state);
    int (*fixup_destroy) (void *addr, enum debug_obj_state state);
    int (*fixup_free) (void *addr, enum debug_obj_state state);
    + int (*fixup_assert_init)(void *addr, enum debug_obj_state state);
    };

    #ifdef CONFIG_DEBUG_OBJECTS
    @@ -64,6 +67,7 @@ extern void debug_object_activate (void *addr, struct debug_obj_descr *descr);
    extern void debug_object_deactivate(void *addr, struct debug_obj_descr *descr);
    extern void debug_object_destroy (void *addr, struct debug_obj_descr *descr);
    extern void debug_object_free (void *addr, struct debug_obj_descr *descr);
    +extern void debug_object_assert_init(void *addr, struct debug_obj_descr *descr);

    /*
    * Active state:
    @@ -89,6 +93,8 @@ static inline void
    debug_object_destroy (void *addr, struct debug_obj_descr *descr) { }
    static inline void
    debug_object_free (void *addr, struct debug_obj_descr *descr) { }
    +static inline void
    +debug_object_assert_init(void *addr, struct debug_obj_descr *descr) { }

    static inline void debug_objects_early_init(void) { }
    static inline void debug_objects_mem_init(void) { }
    diff --git a/lib/debugobjects.c b/lib/debugobjects.c
    index 0b07cc5..be066fa 100644
    --- a/lib/debugobjects.c
    +++ b/lib/debugobjects.c
    @@ -570,6 +570,44 @@ out_unlock:
    }

    /**
    + * debug_object_assert_init - debug checks when object should be init-ed
    + * @addr: address of the object
    + * @descr: pointer to an object specific debug description structure
    + */
    +void debug_object_assert_init(void *addr, struct debug_obj_descr *descr)
    +{
    + struct debug_bucket *db;
    + struct debug_obj *obj;
    + unsigned long flags;
    +
    + if (!debug_objects_enabled)
    + return;
    +
    + db = get_bucket((unsigned long) addr);
    +
    + raw_spin_lock_irqsave(&db->lock, flags);
    +
    + obj = lookup_object(addr, db);
    + if (!obj) {
    + struct debug_obj o = { .object = addr,
    + .state = ODEBUG_STATE_NOTAVAILABLE,
    + .descr = descr };
    +
    + raw_spin_unlock_irqrestore(&db->lock, flags);
    + /*
    + * Maybe the object is static. Let the type specific
    + * code decide what to do.
    + */
    + if (debug_object_fixup(descr->fixup_assert_init, addr,
    + ODEBUG_STATE_NOTAVAILABLE))
    + debug_print_object(&o, "assert_init");
    + return;
    + }
    +
    + raw_spin_unlock_irqrestore(&db->lock, flags);
    +}
    +
    +/**
    * debug_object_active_state - debug checks object usage state machine
    * @addr: address of the object
    * @descr: pointer to an object specific debug description structure
    --
    Sent by an employee of the Qualcomm Innovation Center, Inc.
    The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.


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