From: Zefan Li Date: Thu, 25 Sep 2014 01:41:02 +0000 (+0800) Subject: cpuset: PF_SPREAD_PAGE and PF_SPREAD_SLAB should be atomic flags X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=eb33a02fddad907cea8b2c4ec3b49835b12d0107 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 Cc: Ingo Molnar Cc: Miao Xie Cc: Kees Cook Fixes: 950592f7b991 ("cpusets: update tasks' page/slab spread flags in time") Reported-by: Tetsuo Handa Signed-off-by: Zefan Li Signed-off-by: Tejun Heo [lizf: Backported to 3.4: - adjust context - check current->flags & PF_MEMPOLICY rather than current->mempolicy] Signed-off-by: Ben Hutchings --- 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) } #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. * 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); 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); } /* 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) #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. @@ -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;