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authorZefan Li <lizefan@huawei.com>2014-09-25 09:41:02 +0800
committerBen Hutchings <ben@decadent.org.uk>2017-10-12 15:27:22 +0100
commiteb33a02fddad907cea8b2c4ec3b49835b12d0107 (patch)
parent4fce5e64991fc0a02e47e525ce72f33def17b7ef (diff)
cpuset: PF_SPREAD_PAGE and PF_SPREAD_SLAB should be atomic flags
commit 2ad654bc5e2b211e92f66da1d819e47d79a866f0 upstream. When we change cpuset.memory_spread_{page,slab}, cpuset will flip PF_SPREAD_{PAGE,SLAB} bit of tsk->flags for each task in that cpuset. This should be done using atomic bitops, but currently we don't, which is broken. Tetsuo reported a hard-to-reproduce kernel crash on RHEL6, which happened when one thread tried to clear PF_USED_MATH while at the same time another thread tried to flip PF_SPREAD_PAGE/PF_SPREAD_SLAB. They both operate on the same task. Here's the full report: https://lkml.org/lkml/2014/9/19/230 To fix this, we make PF_SPREAD_PAGE and PF_SPREAD_SLAB atomic flags. v4: - updated mm/slab.c. (Fengguang Wu) - updated Documentation. Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Miao Xie <miaox@cn.fujitsu.com> Cc: Kees Cook <keescook@chromium.org> Fixes: 950592f7b991 ("cpusets: update tasks' page/slab spread flags in time") Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Zefan Li <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> [lizf: Backported to 3.4: - adjust context - check current->flags & PF_MEMPOLICY rather than current->mempolicy] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
5 files changed, 22 insertions, 13 deletions
diff --git a/Documentation/cgroups/cpusets.txt b/Documentation/cgroups/cpusets.txt
index 5c51ed406d1d..eedecbbaac57 100644
--- a/Documentation/cgroups/cpusets.txt
+++ b/Documentation/cgroups/cpusets.txt
@@ -345,14 +345,14 @@ the named feature on.
The implementation is simple.
Setting the flag 'cpuset.memory_spread_page' turns on a per-process flag
-PF_SPREAD_PAGE for each task that is in that cpuset or subsequently
+PFA_SPREAD_PAGE for each task that is in that cpuset or subsequently
joins that cpuset. The page allocation calls for the page cache
-is modified to perform an inline check for this PF_SPREAD_PAGE task
+is modified to perform an inline check for this PFA_SPREAD_PAGE task
flag, and if set, a call to a new routine cpuset_mem_spread_node()
returns the node to prefer for the allocation.
Similarly, setting 'cpuset.memory_spread_slab' turns on the flag
-PF_SPREAD_SLAB, and appropriately marked slab caches will allocate
+PFA_SPREAD_SLAB, and appropriately marked slab caches will allocate
pages from the node returned by cpuset_mem_spread_node().
The cpuset_mem_spread_node() routine is also simple. It uses the
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 7a7e5fd2a277..1dc942705235 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -74,12 +74,12 @@ extern int cpuset_slab_spread_node(void);
static inline int cpuset_do_page_mem_spread(void)
- return current->flags & PF_SPREAD_PAGE;
+ return task_spread_page(current);
static inline int cpuset_do_slab_mem_spread(void)
- return current->flags & PF_SPREAD_SLAB;
+ return task_spread_slab(current);
extern int current_cpuset_is_being_rebound(void);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a0ec63408371..2d4ab762d479 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1812,8 +1812,6 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
#define PF_RANDOMIZE 0x00400000 /* randomize virtual address space */
#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
-#define PF_SPREAD_PAGE 0x01000000 /* Spread page cache over cpuset */
-#define PF_SPREAD_SLAB 0x02000000 /* Spread some slab caches over cpuset */
#define PF_THREAD_BOUND 0x04000000 /* Thread bound to specific cpu */
#define PF_MCE_EARLY 0x08000000 /* Early kill for mce process policy */
#define PF_MEMPOLICY 0x10000000 /* Non-default NUMA mempolicy */
@@ -1847,6 +1845,8 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
#define used_math() tsk_used_math(current)
/* Per-process atomic flags. */
+#define PFA_SPREAD_PAGE 1 /* Spread page cache over cpuset */
+#define PFA_SPREAD_SLAB 2 /* Spread some slab caches over cpuset */
#define TASK_PFA_TEST(name, func) \
static inline bool task_##func(struct task_struct *p) \
@@ -1950,6 +1950,14 @@ static inline int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask)
* Do not use outside of architecture code which knows its limitations.
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 4346f9a2c9dc..5cc0eece8e3a 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -326,13 +326,14 @@ static void cpuset_update_task_spread_flag(struct cpuset *cs,
struct task_struct *tsk)
if (is_spread_page(cs))
- tsk->flags |= PF_SPREAD_PAGE;
+ task_set_spread_page(tsk);
- tsk->flags &= ~PF_SPREAD_PAGE;
+ task_clear_spread_page(tsk);
if (is_spread_slab(cs))
- tsk->flags |= PF_SPREAD_SLAB;
+ task_set_spread_slab(tsk);
- tsk->flags &= ~PF_SPREAD_SLAB;
+ task_clear_spread_slab(tsk);
diff --git a/mm/slab.c b/mm/slab.c
index aea5e42c67d8..bb39255d8b3f 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3255,7 +3255,7 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
- * Try allocating on another node if PF_SPREAD_SLAB|PF_MEMPOLICY.
+ * Try allocating on another node if PFA_SPREAD_SLAB|PF_MEMPOLICY.
* If we are in_interrupt, then process context, including cpusets and
* mempolicy, may not apply and should not be used for allocation policy.
@@ -3496,7 +3496,7 @@ __do_cache_alloc(struct kmem_cache *cache, gfp_t flags)
void *objp;
- if (unlikely(current->flags & (PF_SPREAD_SLAB | PF_MEMPOLICY))) {
+ if (unlikely((current->flags & PF_MEMPOLICY) || cpuset_do_slab_mem_spread())) {
objp = alternate_node_alloc(cache, flags);
if (objp)
goto out;