Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 568dca15 authored by Stephen Boyd's avatar Stephen Boyd Committed by Russell King
Browse files

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



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: default avatarStephen Boyd <sboyd@codeaurora.org>
Reported-by: default avatarPatrik Kluba <pkluba@dension.com>
Tested-by: default avatarPatrik Kluba <pkluba@dension.com>
Cc: <stable@vger.kernel.org> # 2.6.30
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 8a3a180d

arch/arm/vfp/entry.S

+3 −3
Original line number Diff line number Diff line
@@ -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

arch/arm/vfp/vfphw.S

+2 −2
Original line number Diff line number Diff line
@@ -168,7 +168,7 @@ 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
@@ -192,7 +192,7 @@ 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