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    SubjectRe: [PATCH] ACPICA: don't cond_resched() when irq_disabled or in_atomic
    Hi Pavel,

    Please elaborate... Your comments "ugly as hell" are too often to be
    specific...
    There is only one use of ACPI_PREEMPTION_POINT(), and it is in the
    ACPICA code,
    which we all agreed to keep OS independent, thus the need for #define.
    Do you see any other way to add preemption point without introducing
    Linux-specific
    code into ACPICA?

    Thanks,
    Alex.


    Pavel Machek пишет:
    > On Fri 2009-12-04 12:26:00, Xiaotian Feng wrote:
    >
    >> commit 8bd108d adds preemption point after each opcode parse, then
    >> a sleeping function called from invalid context bug was founded
    >> during suspend/resume stage. this was fixed in commit abe1dfa by
    >> don't cond_resched when irq_disabled. But recent commit 138d156 changes
    >> the behaviour to don't cond_resched when in_atomic. This makes the
    >> sleeping function called from invalid context bug happen again, which
    >> is reported in http://lkml.org/lkml/2009/12/1/371.
    >>
    >> The fix is to cond_sched() only when preemptible, which means not in
    >> irq_disabled or in_atomic.
    >>
    >> @@ -152,7 +152,7 @@ static inline void *acpi_os_acquire_object(acpi_cache_t * cache)
    >> #include <linux/hardirq.h>
    >> #define ACPI_PREEMPTION_POINT() \
    >> do { \
    >> - if (!in_atomic_preempt_off()) \
    >> + if (preemptible()) \
    >> cond_resched(); \
    >> } while (0)
    >>
    >
    > Note that this is ugly as hell. It means we have two acpi
    > interpretters in kernel, one for preemptible, one for non-preemptible,
    > with very different behaviour.
    >
    > It would be slightly nicer to pass the "preemptible" info explicitely,
    > as function parameters.
    >
    > It would be even better not to need that difference.
    >
    > Pavel
    >

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