From a2609f9676974198505ae836ee81a4c863c33c60 Mon Sep 17 00:00:00 2001 From: Xiao Guangrong Date: Fri, 28 Sep 2012 10:19:16 +1000 Subject: [PATCH] thp: move khugepaged_mutex out of khugepaged Currently, hugepaged_mutex is used really complexly and hard to understand, actually, it is just used to serialize start_khugepaged and khugepaged for these reasons: - khugepaged_thread is shared between them - the thp disable path (echo never > transparent_hugepage/enabled) is nonblocking, so we need to protect khugepaged_thread to get a stable running state These can be avoided by: - use the lock to serialize the thread creation and cancel - thp disable path can not finised until the thread exits Then khugepaged_thread is fully controlled by start_khugepaged, khugepaged will be happy without the lock Signed-off-by: Xiao Guangrong Cc: Andrea Arcangeli Cc: Hugh Dickins Cc: David Rientjes Signed-off-by: Andrew Morton --- mm/huge_memory.c | 36 +++++++++++++----------------------- 1 file changed, 13 insertions(+), 23 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f24bc6521779..295f6ceebe05 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -140,9 +140,6 @@ static int start_khugepaged(void) { int err = 0; if (khugepaged_enabled()) { - int wakeup; - - mutex_lock(&khugepaged_mutex); if (!khugepaged_thread) khugepaged_thread = kthread_run(khugepaged, NULL, "khugepaged"); @@ -152,15 +149,17 @@ static int start_khugepaged(void) err = PTR_ERR(khugepaged_thread); khugepaged_thread = NULL; } - wakeup = !list_empty(&khugepaged_scan.mm_head); - mutex_unlock(&khugepaged_mutex); - if (wakeup) + + if (!list_empty(&khugepaged_scan.mm_head)) wake_up_interruptible(&khugepaged_wait); set_recommended_min_free_kbytes(); - } else + } else if (khugepaged_thread) { /* wakeup to exit */ wake_up_interruptible(&khugepaged_wait); + kthread_stop(khugepaged_thread); + khugepaged_thread = NULL; + } return err; } @@ -222,7 +221,12 @@ static ssize_t enabled_store(struct kobject *kobj, TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); if (ret > 0) { - int err = start_khugepaged(); + int err; + + mutex_lock(&khugepaged_mutex); + err = start_khugepaged(); + mutex_unlock(&khugepaged_mutex); + if (err) ret = err; } @@ -2412,20 +2416,10 @@ static int khugepaged(void *none) set_freezable(); set_user_nice(current, 19); - /* serialize with start_khugepaged() */ - mutex_lock(&khugepaged_mutex); - - for (;;) { - mutex_unlock(&khugepaged_mutex); + while (!kthread_should_stop()) { VM_BUG_ON(khugepaged_thread != current); khugepaged_loop(); VM_BUG_ON(khugepaged_thread != current); - - mutex_lock(&khugepaged_mutex); - if (!khugepaged_enabled()) - break; - if (unlikely(kthread_should_stop())) - break; } spin_lock(&khugepaged_mm_lock); @@ -2434,10 +2428,6 @@ static int khugepaged(void *none) if (mm_slot) collect_mm_slot(mm_slot); spin_unlock(&khugepaged_mm_lock); - - khugepaged_thread = NULL; - mutex_unlock(&khugepaged_mutex); - return 0; } -- 2.39.5