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Commit 2dd17030 authored by Leonid Yegoshin's avatar Leonid Yegoshin Committed by Ralf Baechle
Browse files

MIPS: Fix race condition with FPU thread task flag during context switch. 



[ralf@linux-mips.org: Cosmetic changes; also fixed up r2300_switch.S and
octeon_switch.S which needed similar modifications.]

Signed-off-by: default avatarLeonid Yegoshin <yegoshin@mips.com>
Signed-off-by: default avatarSteven J. Hill <sjhill@mips.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3784/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent dc34b05f

arch/mips/include/asm/switch_to.h

+4 −2
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ struct task_struct; 
 * switch_to(n) should switch tasks to task nr n, first

 * checking that n isn't the current task, in which case it does nothing.

 */

extern asmlinkage void *resume(void *last, void *next, void *next_ti);

extern asmlinkage void *resume(void *last, void *next, void *next_ti, u32 __usedfpu);



extern unsigned int ll_bit;

extern struct task_struct *ll_task;
@@ -66,11 +66,13 @@ do { \ 


#define switch_to(prev, next, last)					\

do {									\

	u32 __usedfpu;							\

	__mips_mt_fpaff_switch_to(prev);				\

	if (cpu_has_dsp)						\

		__save_dsp(prev);					\

	__clear_software_ll_bit();					\

	(last) = resume(prev, next, task_thread_info(next));		\

	__usedfpu = test_and_clear_tsk_thread_flag(prev, TIF_USEDFPU);	\

	(last) = resume(prev, next, task_thread_info(next), __usedfpu);	\

} while (0)



#define finish_arch_switch(prev)					\

arch/mips/kernel/octeon_switch.S

+1 −1
Original line number Diff line number Diff line
@@ -31,7 +31,7 @@ 


/*

 * task_struct *resume(task_struct *prev, task_struct *next,

 *                     struct thread_info *next_ti)

 *                     struct thread_info *next_ti, int usedfpu)

 */

	.align	7

	LEAF(resume)

arch/mips/kernel/r2300_switch.S

+3 −12
Original line number Diff line number Diff line
@@ -43,7 +43,7 @@ 


/*

 * task_struct *resume(task_struct *prev, task_struct *next,

 *                     struct thread_info *next_ti) )

 *                     struct thread_info *next_ti, int usedfpu)

 */

LEAF(resume)

	mfc0	t1, CP0_STATUS
@@ -51,18 +51,9 @@ LEAF(resume) 
	cpu_save_nonscratch a0

	sw	ra, THREAD_REG31(a0)



	/*

	 * check if we need to save FPU registers

	 */

	lw	t3, TASK_THREAD_INFO(a0)

	lw	t0, TI_FLAGS(t3)

	li	t1, _TIF_USEDFPU

	and	t2, t0, t1

	beqz	t2, 1f

	nor	t1, zero, t1

	beqz	a3, 1f



	and	t0, t0, t1

	sw	t0, TI_FLAGS(t3)

	PTR_L	t3, TASK_THREAD_INFO(a0)



	/*

	 * clear saved user stack CU1 bit

arch/mips/kernel/r4k_switch.S

+3 −9
Original line number Diff line number Diff line
@@ -41,7 +41,7 @@ 


/*

 * task_struct *resume(task_struct *prev, task_struct *next,

 *                     struct thread_info *next_ti)

 *                     struct thread_info *next_ti, int usedfpu)

 */

	.align	5

	LEAF(resume)
@@ -53,16 +53,10 @@ 
	/*

	 * check if we need to save FPU registers

	 */

	PTR_L	t3, TASK_THREAD_INFO(a0)

	LONG_L	t0, TI_FLAGS(t3)

	li	t1, _TIF_USEDFPU

	and	t2, t0, t1

	beqz	t2, 1f

	nor	t1, zero, t1



	and	t0, t0, t1

	LONG_S	t0, TI_FLAGS(t3)

	beqz    a3, 1f



	PTR_L	t3, TASK_THREAD_INFO(a0)

	/*

	 * clear saved user stack CU1 bit

	 */