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authorXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>2012-10-08 16:29:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-09 16:22:25 +0900
commit911891afe1c3104adf0f802189909868239ebbfd (patch)
tree8583f33ded3ef14a85fe7cd2244c605ece673f37 /mm/huge_memory.c
parent637e3a27ec2c84f7ecd083fa6943da2f19eb5e9f (diff)
downloadlinux-911891afe1c3104adf0f802189909868239ebbfd.tar.bz2
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 <xiaoguangrong@linux.vnet.ibm.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r--mm/huge_memory.c36
1 files changed, 13 insertions, 23 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9833d8ecf38f..0931b2b19c52 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -139,9 +139,6 @@ 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");
@@ -151,15 +148,17 @@ 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;
}
@@ -221,7 +220,12 @@ 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;
}
@@ -2329,20 +2333,10 @@ 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);
@@ -2351,10 +2345,6 @@ 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;
}