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ARM: 7627/1: Predicate preempt logic on PREEMP_COUNT not PREEMPT alone

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commit 568dca15aa upstream.

Patrik Kluba reports that the preempt count becomes invalid due
to the preempt_enable() call being unbalanced with a
preempt_disable() call in the vfp assembly routines. This happens
because preempt_enable() and preempt_disable() update preempt
counts under PREEMPT_COUNT=y but the vfp assembly routines do so
under PREEMPT=y. In a configuration where PREEMPT=n and
DEBUG_ATOMIC_SLEEP=y, PREEMPT_COUNT=y and so the preempt_enable()
call in VFP_bounce() keeps subtracting from the preempt count
until it goes negative.

Fix this by always using PREEMPT_COUNT to decided when to update
preempt counts in the ARM assembly code.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Reported-by: Patrik Kluba <pkluba@dension.com>
Tested-by: Patrik Kluba <pkluba@dension.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Stephen Boyd 2013-01-14 19:50:42 +01:00 committed by Greg Kroah-Hartman
parent 399f41521e
commit 112ae50d21
2 changed files with 5 additions and 5 deletions
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6
arch/arm/vfp/entry.S
View File

@ -22,7 +22,7 @@
@ IRQs disabled.
@
ENTRY(do_vfp)
#ifdef CONFIG_PREEMPT
#ifdef CONFIG_PREEMPT_COUNT
ldr r4, [r10, #TI_PREEMPT] @ get preempt count
add r11, r4, #1 @ increment it
str r11, [r10, #TI_PREEMPT]
@ -35,7 +35,7 @@ ENTRY(do_vfp)
ENDPROC(do_vfp)
ENTRY(vfp_null_entry)
#ifdef CONFIG_PREEMPT
#ifdef CONFIG_PREEMPT_COUNT
get_thread_info r10
ldr r4, [r10, #TI_PREEMPT] @ get preempt count
sub r11, r4, #1 @ decrement it
@ -53,7 +53,7 @@ ENDPROC(vfp_null_entry)
__INIT
ENTRY(vfp_testing_entry)
#ifdef CONFIG_PREEMPT
#ifdef CONFIG_PREEMPT_COUNT
get_thread_info r10
ldr r4, [r10, #TI_PREEMPT] @ get preempt count
sub r11, r4, #1 @ decrement it

4
arch/arm/vfp/vfphw.S
View File

@ -167,7 +167,7 @@ vfp_hw_state_valid:
@ else it's one 32-bit instruction, so
@ always subtract 4 from the following
@ instruction address.
#ifdef CONFIG_PREEMPT
#ifdef CONFIG_PREEMPT_COUNT
get_thread_info r10
ldr r4, [r10, #TI_PREEMPT] @ get preempt count
sub r11, r4, #1 @ decrement it
@ -191,7 +191,7 @@ look_for_VFP_exceptions:
@ not recognised by VFP
DBGSTR "not VFP"
#ifdef CONFIG_PREEMPT
#ifdef CONFIG_PREEMPT_COUNT
get_thread_info r10
ldr r4, [r10, #TI_PREEMPT] @ get preempt count
sub r11, r4, #1 @ decrement it