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ARM: 7790/1: Fix deferred mm switch on VIVT processors 

As of commit b9d4d42ad9 (ARM: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW on
pre-ARMv6 CPUs), the mm switching on VIVT processors is done in the
finish_arch_post_lock_switch() function to avoid whole cache flushing
with interrupts disabled. The need for deferred mm switch is stored as a
thread flag (TIF_SWITCH_MM). However, with preemption enabled, we can
have another thread switch before finish_arch_post_lock_switch(). If the
new thread has the same mm as the previous 'next' thread, the scheduler
will not call switch_mm() and the TIF_SWITCH_MM flag won't be set for
the new thread.

This patch moves the switch pending flag to the mm_context_t structure
since this is specific to the mm rather than thread.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Tested-by: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: <stable@vger.kernel.org> # 3.5+
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Catalin Marinas 2013-07-23 16:15:36 +01:00 committed by Russell King
parent 1f49856bb0
commit bdae73cd37
3 changed files with 18 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/arm/include/asm/mmu.h
View File

@ -6,6 +6,8 @@
typedef struct {
#ifdef CONFIG_CPU_HAS_ASID
atomic64_t id;
#else
int switch_pending;
#endif
unsigned int vmalloc_seq;
} mm_context_t;

20
arch/arm/include/asm/mmu_context.h
View File

@ -56,7 +56,7 @@ static inline void check_and_switch_context(struct mm_struct *mm,
* on non-ASID CPUs, the old mm will remain valid until the
* finish_arch_post_lock_switch() call.
*/
set_ti_thread_flag(task_thread_info(tsk), TIF_SWITCH_MM);
mm->context.switch_pending = 1;
else
cpu_switch_mm(mm->pgd, mm);
}
@ -65,9 +65,21 @@ static inline void check_and_switch_context(struct mm_struct *mm,
finish_arch_post_lock_switch
static inline void finish_arch_post_lock_switch(void)
{
if (test_and_clear_thread_flag(TIF_SWITCH_MM)) {
struct mm_struct *mm = current->mm;
cpu_switch_mm(mm->pgd, mm);
struct mm_struct *mm = current->mm;
if (mm && mm->context.switch_pending) {
/*
* Preemption must be disabled during cpu_switch_mm() as we
* have some stateful cache flush implementations. Check
* switch_pending again in case we were preempted and the
* switch to this mm was already done.
*/
preempt_disable();
if (mm->context.switch_pending) {
mm->context.switch_pending = 0;
cpu_switch_mm(mm->pgd, mm);
}
preempt_enable_no_resched();
}
}

1
arch/arm/include/asm/thread_info.h
View File

@ -156,7 +156,6 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
#define TIF_USING_IWMMXT 17
#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
#define TIF_RESTORE_SIGMASK 20
#define TIF_SWITCH_MM 22 /* deferred switch_mm */
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)