Messages in this thread | | | From | "Moore, Robert" <> | Date | Mon, 9 Aug 2010 08:56:28 -0700 | Subject | RE: [PATCH] ACPI: Fix wrong atomicity check in preemption point |
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I'll be happy to include this in the aclinux.h file if the day ever comes when it is stable.
>-----Original Message----- >From: Frederic Weisbecker [mailto:fweisbec@gmail.com] >Sent: Friday, August 06, 2010 8:39 PM >To: Brown, Len >Cc: LKML; Frederic Weisbecker; Moore, Robert >Subject: [PATCH] ACPI: Fix wrong atomicity check in preemption point > >The acpi preemption point checks the atomicity of the context >using in_atomic_preempt_off(). This helper must be used only >to check the atomicity before a prior call to preempt_disable(), >which is not what we want here. > >What we want is to simply check if we are in an atomic section. >This helper is actually only used by the scheduler for particular >needs and shouldn't be used outside. > >The check made here is then always wrong. We will schedule only if >preemption has been disabled once. It never has been a problem >during the boot because premption is disabled and moreover the BKL >is held, so we increase twice the preempt count. But now that >we drop the bkl from the boot, the preempt count is only increased >once, and then we schedule in the acpi preemption point while we >shouldn't. > >In fact using such in_atomic*() like helpers is quite fragile to >guess if we can schedule, but still, in_atomic() is less buggy than >what was there before. > >This fixes: > >[ 0.008086] BUG: scheduling while atomic: swapper/0/0x10000002 >[ 0.008167] no locks held by swapper/0. >[ 0.008243] Modules linked in: >[ 0.008356] Pid: 0, comm: swapper Not tainted 2.6.35+ #793 >[ 0.008437] Call Trace: >[ 0.008519] [<ffffffff8106eab3>] ? __debug_show_held_locks+0x13/0x30 >[ 0.008605] [<ffffffff81039a65>] __schedule_bug+0x85/0x90 >[ 0.008690] [<ffffffff815edf20>] schedule+0x670/0x840 >[ 0.008775] [<ffffffff8129ff88>] ? acpi_os_release_object+0x9/0xd >[ 0.008860] [<ffffffff812beca0>] ? acpi_ps_free_op+0x22/0x24 >[ 0.008944] [<ffffffff8103ccd5>] __cond_resched+0x25/0x40 >[ 0.009008] [<ffffffff815ee1ed>] _cond_resched+0x2d/0x40 >[ 0.009091] [<ffffffff812bdf4a>] acpi_ps_complete_op+0x292/0x2a8 >[ 0.009174] [<ffffffff812be7b6>] acpi_ps_parse_loop+0x856/0x9ac >[ 0.010008] [<ffffffff812bd81d>] acpi_ps_parse_aml+0x9a/0x2b9 >[ 0.010092] [<ffffffff812bc048>] acpi_ns_one_complete_parse+0xfc/0x117 >[ 0.010176] [<ffffffff812bc07f>] acpi_ns_parse_table+0x1c/0x35 >[ 0.010259] [<ffffffff812b9606>] acpi_ns_load_table+0x4a/0x8c >[ 0.010343] [<ffffffff812c075f>] acpi_load_tables+0xa0/0x164 >[ 0.010429] [<ffffffff819751e1>] ? acpi_initialize_subsystem+0x69/0x91 >[ 0.010513] [<ffffffff819740df>] acpi_early_init+0x6c/0xf7 >[ 0.010598] [<ffffffff8194fd68>] start_kernel+0x3b3/0x3fb >[ 0.010681] [<ffffffff8194f26d>] x86_64_start_reservations+0x7d/0x89 >[ 0.010765] [<ffffffff8194f359>] x86_64_start_kernel+0xe0/0xf2 > >Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> >Cc: Bob Moore <robert.moore@intel.com> >--- > include/acpi/platform/aclinux.h | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > >diff --git a/include/acpi/platform/aclinux.h >b/include/acpi/platform/aclinux.h >index e5039a2..8da1e8c 100644 >--- a/include/acpi/platform/aclinux.h >+++ b/include/acpi/platform/aclinux.h >@@ -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() && !irqs_disabled()) \ >+ if (!in_atomic() && !irqs_disabled()) \ > cond_resched(); \ > } while (0) > >-- >1.6.2.3
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