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cpuset: PF_SPREAD_PAGE and PF_SPREAD_SLAB should be atomic flags

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commit 2ad654bc5e 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: 950592f7b9 ("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]
This commit is contained in:
Zefan Li 2014-09-25 09:41:02 +08:00
parent 699c06b386
commit 4fae6ccac6
5 changed files with 22 additions and 13 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
Documentation/cgroups/cpusets.txt
View file

@ -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

4
include/linux/cpuset.h
View file

@ -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);

12
include/linux/sched.h
View file

@ -1834,8 +1834,6 @@ 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 */
@ -1868,6 +1866,8 @@ 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) \
@ -1970,6 +1970,14 @@ static inline int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask)
}
#endif
TASK_PFA_TEST(SPREAD_PAGE, spread_page)
TASK_PFA_SET(SPREAD_PAGE, spread_page)
TASK_PFA_CLEAR(SPREAD_PAGE, spread_page)
TASK_PFA_TEST(SPREAD_SLAB, spread_slab)
TASK_PFA_SET(SPREAD_SLAB, spread_slab)
TASK_PFA_CLEAR(SPREAD_SLAB, spread_slab)
/*
* Do not use outside of architecture code which knows its limitations.
*

9
kernel/cpuset.c
View file

@ -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);
else
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);
else
tsk->flags &= ~PF_SPREAD_SLAB;
task_clear_spread_slab(tsk);
}
/*

4
mm/slab.c
View file

@ -3321,7 +3321,7 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
#ifdef CONFIG_NUMA
/*
* 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.
@ -3562,7 +3562,7 @@ __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;