From bdae73cd374e28db544fdd9b77de689a36e3c129 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Tue, 23 Jul 2013 16:15:36 +0100 Subject: 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_context.h | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) (limited to 'arch/arm/include/asm/mmu_context.h') 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(); } } -- cgit v1.2.3