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Date: Thu, 7 Jul 2016 18:29:58 +0900
From: Byungchul Park <byungchul.park@....com>
To: peterz@...radead.org, mingo@...nel.org
Cc: tglx@...utronix.de, npiggin@...nel.dk, walken@...gle.com,
boqun.feng@...il.com, kirill@...temov.name,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [RFC v2 08/13] lockdep: Apply crossrelease to PG_locked lock
lock_page() and its family can cause deadlock. Nevertheless, it cannot
use the lock correctness validator becasue unlock_page() can be called
in different context from the context calling lock_page(), which
violates original lockdep's assumption.
However, thanks to CONFIG_LOCKDEP_CROSSRELEASE, we can apply the lockdep
detector to lock_page() using PG_locked. Applied it.
Signed-off-by: Byungchul Park <byungchul.park@....com>
---
include/linux/mm_types.h | 9 +++++
include/linux/pagemap.h | 95 +++++++++++++++++++++++++++++++++++++++++++++---
lib/Kconfig.debug | 9 +++++
mm/filemap.c | 4 +-
mm/page_alloc.c | 3 ++
5 files changed, 112 insertions(+), 8 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 624b78b..ab33ee3 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -15,6 +15,10 @@
#include <asm/page.h>
#include <asm/mmu.h>
+#ifdef CONFIG_LOCKDEP_PAGELOCK
+#include <linux/lockdep.h>
+#endif
+
#ifndef AT_VECTOR_SIZE_ARCH
#define AT_VECTOR_SIZE_ARCH 0
#endif
@@ -215,6 +219,11 @@ struct page {
#ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
int _last_cpupid;
#endif
+
+#ifdef CONFIG_LOCKDEP_PAGELOCK
+ struct lockdep_map map;
+ struct cross_lock xlock;
+#endif
}
/*
* The struct page can be forced to be double word aligned so that atomic ops
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index c0049d9..2fc4af1 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -14,6 +14,9 @@
#include <linux/bitops.h>
#include <linux/hardirq.h> /* for in_interrupt() */
#include <linux/hugetlb_inline.h>
+#ifdef CONFIG_LOCKDEP_PAGELOCK
+#include <linux/lockdep.h>
+#endif
/*
* Bits in mapping->flags. The lower __GFP_BITS_SHIFT bits are the page
@@ -441,26 +444,81 @@ static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
return pgoff >> (PAGE_CACHE_SHIFT - PAGE_SHIFT);
}
+#ifdef CONFIG_LOCKDEP_PAGELOCK
+#define lock_page_init(p) \
+do { \
+ static struct lock_class_key __key; \
+ lockdep_init_map_crosslock(&(p)->map, &(p)->xlock, \
+ "(PG_locked)" #p, &__key, 0); \
+} while (0)
+
+static inline void lock_page_acquire(struct page *page, int try)
+{
+ page = compound_head(page);
+ lock_acquire_exclusive(&page->map, 0, try, NULL, _RET_IP_);
+}
+
+static inline void lock_page_release(struct page *page)
+{
+ page = compound_head(page);
+ /*
+ * Calling lock_commit_crosslock() is necessary
+ * for cross-releasable lock when the lock is
+ * releasing before calling lock_release().
+ */
+ lock_commit_crosslock(&page->map);
+ lock_release(&page->map, 0, _RET_IP_);
+}
+#else
+static inline void lock_page_init(struct page *page) {}
+static inline void lock_page_free(struct page *page) {}
+static inline void lock_page_acquire(struct page *page, int try) {}
+static inline void lock_page_release(struct page *page) {}
+#endif
+
extern void __lock_page(struct page *page);
extern int __lock_page_killable(struct page *page);
extern int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
unsigned int flags);
-extern void unlock_page(struct page *page);
+extern void do_raw_unlock_page(struct page *page);
-static inline int trylock_page(struct page *page)
+static inline void unlock_page(struct page *page)
+{
+ lock_page_release(page);
+ do_raw_unlock_page(page);
+}
+
+static inline int do_raw_trylock_page(struct page *page)
{
page = compound_head(page);
return (likely(!test_and_set_bit_lock(PG_locked, &page->flags)));
}
+static inline int trylock_page(struct page *page)
+{
+ if (do_raw_trylock_page(page)) {
+ lock_page_acquire(page, 1);
+ return 1;
+ }
+ return 0;
+}
+
/*
* lock_page may only be called if we have the page's inode pinned.
*/
static inline void lock_page(struct page *page)
{
might_sleep();
- if (!trylock_page(page))
+
+ if (!do_raw_trylock_page(page))
__lock_page(page);
+ /*
+ * The acquire function must be after actual lock operation
+ * for crossrelease lock, because the lock instance is
+ * searched by release operation in any context and more
+ * than two instances acquired make it confused.
+ */
+ lock_page_acquire(page, 0);
}
/*
@@ -470,9 +528,22 @@ static inline void lock_page(struct page *page)
*/
static inline int lock_page_killable(struct page *page)
{
+ int ret;
+
might_sleep();
- if (!trylock_page(page))
- return __lock_page_killable(page);
+
+ if (!do_raw_trylock_page(page)) {
+ ret = __lock_page_killable(page);
+ if (ret)
+ return ret;
+ }
+ /*
+ * The acquire function must be after actual lock operation
+ * for crossrelease lock, because the lock instance is
+ * searched by release operation in any context and more
+ * than two instances acquired make it confused.
+ */
+ lock_page_acquire(page, 0);
return 0;
}
@@ -487,7 +558,19 @@ static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
unsigned int flags)
{
might_sleep();
- return trylock_page(page) || __lock_page_or_retry(page, mm, flags);
+
+ if (do_raw_trylock_page(page) || __lock_page_or_retry(page, mm, flags)) {
+ /*
+ * The acquire function must be after actual lock operation
+ * for crossrelease lock, because the lock instance is
+ * searched by release operation in any context and more
+ * than two instances acquired make it confused.
+ */
+ lock_page_acquire(page, 0);
+ return 1;
+ }
+
+ return 0;
}
/*
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index b5946c7..ee7faca 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1014,6 +1014,15 @@ config LOCKDEP_COMPLETE
A deadlock caused by wait and complete can be detected by lockdep
using crossrelease feature.
+config LOCKDEP_PAGELOCK
+ bool "Lock debugging: allow PG_locked lock to use deadlock detector"
+ select LOCKDEP_CROSSRELEASE
+ default n
+ help
+ PG_locked lock is a kind of cross-released lock. This makes
+ PG_locked lock possible to use deadlock detector, using
+ crossrelease feature.
+
config PROVE_LOCKING
bool "Lock debugging: prove locking correctness"
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
diff --git a/mm/filemap.c b/mm/filemap.c
index 3461d97..47fc5c0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -814,7 +814,7 @@ EXPORT_SYMBOL_GPL(add_page_wait_queue);
* The mb is necessary to enforce ordering between the clear_bit and the read
* of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
*/
-void unlock_page(struct page *page)
+void do_raw_unlock_page(struct page *page)
{
page = compound_head(page);
VM_BUG_ON_PAGE(!PageLocked(page), page);
@@ -822,7 +822,7 @@ void unlock_page(struct page *page)
smp_mb__after_atomic();
wake_up_page(page, PG_locked);
}
-EXPORT_SYMBOL(unlock_page);
+EXPORT_SYMBOL(do_raw_unlock_page);
/**
* end_page_writeback - end writeback against a page
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 838ca8bb..17ed9a8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4538,6 +4538,9 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
} else {
__init_single_pfn(pfn, zone, nid);
}
+#ifdef CONFIG_LOCKDEP_PAGELOCK
+ lock_page_init(pfn_to_page(pfn));
+#endif
}
}
--
1.9.1
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