[PATCH] ACPI: Fix wrong atomicity check in preemption point

[Frederic Weisbecker]

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@xxxxxxxxx>
Cc: Bob Moore <robert.moore@xxxxxxxxx>
---
 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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