From bdae73cd374e28db544fdd9b77de689a36e3c129 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Tue, 23 Jul 2013 16:15:36 +0100 Subject: [PATCH] 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 Reported-by: Marc Kleine-Budde Tested-by: Marc Kleine-Budde Cc: # 3.5+ Signed-off-by: Russell King --- arch/arm/include/asm/mmu.h | 2 ++ arch/arm/include/asm/mmu_context.h | 20 ++++++++++++++++---- arch/arm/include/asm/thread_info.h | 1 - 3 files changed, 18 insertions(+), 5 deletions(-) diff --git a/arch/arm/include/asm/mmu.h b/arch/arm/include/asm/mmu.h index e3d55547e755..d1b4998e4f43 100644 --- a/arch/arm/include/asm/mmu.h +++ b/arch/arm/include/asm/mmu.h @@ -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; diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h index b5792b7fd8d3..9b32f76bb0dd 100644 --- a/arch/arm/include/asm/mmu_context.h +++ b/arch/arm/include/asm/mmu_context.h @@ -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(); } } diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index 214d4158089a..2b8114fcba09 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -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) -- 2.20.1