[PATCH][retry 1] 2.6.27-rc2: invalidate caches before going into suspend - Kernel

This is a discussion on [PATCH][retry 1] 2.6.27-rc2: invalidate caches before going into suspend - Kernel ; When a CPU core is shut down, all of its caches need to be flushed to prevent stale data from causing errors if the core is resumed. Current Linux suspend code performs an assignment after the flush, which can add ...

+ Reply to Thread
Results 1 to 2 of 2

Thread: [PATCH][retry 1] 2.6.27-rc2: invalidate caches before going into suspend

  1. [PATCH][retry 1] 2.6.27-rc2: invalidate caches before going into suspend

    When a CPU core is shut down, all of its caches need to be flushed
    to prevent stale data from causing errors if the core is resumed.
    Current Linux suspend code performs an assignment after the flush,
    which can add dirty data back to the cache. On some AMD platforms,
    additional speculative reads have caused crashes on resume because
    of this dirty data.

    Relocate the cache flush to be the very last thing done before
    halting.


    Signed-off-by: Mark Langsdorf
    Acked-by: Mark Borden
    Acked-by: Michael Hohmuth

    diff -r 1e74a821dd00 arch/x86/kernel/process_32.c
    --- a/arch/x86/kernel/process_32.c Tue Aug 12 12:04:12 2008 -0500
    +++ b/arch/x86/kernel/process_32.c Wed Aug 13 07:03:35 2008 -0500
    @@ -95,7 +95,6 @@ static inline void play_dead(void)
    {
    /* This must be done before dead CPU ack */
    cpu_exit_clear();
    - wbinvd();
    mb();
    /* Ack it */
    __get_cpu_var(cpu_state) = CPU_DEAD;
    @@ -104,6 +103,7 @@ static inline void play_dead(void)
    * With physical CPU hotplug, we should halt the cpu
    */
    local_irq_disable();
    + wbinvd();
    while (1)
    halt();
    }
    diff -r 1e74a821dd00 arch/x86/kernel/process_64.c
    --- a/arch/x86/kernel/process_64.c Tue Aug 12 12:04:12 2008 -0500
    +++ b/arch/x86/kernel/process_64.c Wed Aug 13 07:03:54 2008 -0500
    @@ -93,12 +93,12 @@ static inline void play_dead(void)
    static inline void play_dead(void)
    {
    idle_task_exit();
    - wbinvd();
    mb();
    /* Ack it */
    __get_cpu_var(cpu_state) = CPU_DEAD;

    local_irq_disable();
    + wbinvd();
    while (1)
    halt();
    }

    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  2. Re: [PATCH][retry 1] 2.6.27-rc2: invalidate caches before going into suspend


    (please keep Cc:s intact)

    * Mark Langsdorf wrote:

    > @@ -104,6 +103,7 @@ static inline void play_dead(void)
    > * With physical CPU hotplug, we should halt the cpu
    > */
    > local_irq_disable();
    > + wbinvd();
    > while (1)
    > halt();

    hm, why not do what i suggested in my first mail:

    if (cpu >= i486)
    asm("cli; wbinvd; cli; 1: hlt; jmp 1b")
    else
    halt();

    perhaps turn it into a wbivd_halt() primitive, to make it clean and even
    more obvious.

    This sequence does matter to reliable suspend/resume, and in theory gcc
    could insert something before a halt() as well.

    [ i only have a pretty far-fetched example that in all likelyhood wont
    happen in practice: for example halt could be decided to be uninlined
    by a braindead compiler, ftrace could hook in there, and dirty some
    state. But still - the point is that we had a difficult bug in this
    code for a long time and in such situations we should just over-do
    robustness by default. ]

    Ingo
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/
+ Reply to Thread
« Re: HPET regression in 2.6.26 versus 2.6.25 -- experimental revert for 2.6.27 failed | [PATCH] /proc/self/maps doesn't display the real file offset »