3.8.13.7 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Catalin Marinas <catalin.marinas@xxxxxxx>
commit bdae73cd374e28db544fdd9b77de689a36e3c129 upstream.
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@xxxxxxx>
Reported-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Tested-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
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 e3d5554..d1b4998 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 863a661..3da6557 100644
--- a/arch/arm/include/asm/mmu_context.h
+++ b/arch/arm/include/asm/mmu_context.h
@@ -45,7 +45,7 @@ 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);
}
@@ -54,9 +54,21 @@ 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 cddda1f..20038ae 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -155,7 +155,6 @@ 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)
--
1.8.1.2
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