sched: fix confusing PFA_NO_NEW_PRIVS constant
Subsystems (5)
PATCH v4 1/3 sched: fix confusing PFA_NO_NEW_PRIVS constant
Commit 1d4457f99928 ("sched: move no_new_privs into new atomic flags") defined PFA_NO_NEW_PRIVS as hexadecimal value, but it is confusing because it is used as bit number. Redefine it as decimal bit number.
Note this changes the bit position of PFA_NOW_NEW_PRIVS from 1 to 0.
Cc Peter Zijlstra <[email protected]>
Cc Ingo Molnar <[email protected]>
Cc Miao Xie <[email protected]>
Signed-off-by Tetsuo Handa <penguin-kernel-JPay3/[email protected]>
Acked-by Kees Cook <[email protected]>
[ lizf: slightly modified subject and changelog ]
Signed-off-by Zefan Li <[email protected]>
--- include/linux/sched.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
include/linux/sched.h +1 -1
@@ -1957,7 +1957,7 @@ static inline void memalloc_noio_restore(unsigned int flags) }/* Per-process atomic flags. */ -#define PFA_NO_NEW_PRIVS 0x00000001/* May not gain new privileges. */ +#define PFA_NO_NEW_PRIVS 0/* May not gain new privileges. */ static inline bool task_no_new_privs (struct task_struct *p) {
Signature · 1 line
1.8.0.2
PATCH v4 2/3 sched: add macros to define bitops for task atomic flags
This will simplify code when we add new flags.
v3:
- Kees pointed out that no_new_privs should never be cleared, so we shouldn't define task_clear_no_new_privs(). we define 3 macros instead of a single one.
v2:
- updated scripts/tags.sh, suggested by Peter
Cc Ingo Molnar <[email protected]>
Cc Miao Xie <[email protected]>
Cc Tetsuo Handa <penguin-kernel-JPay3/[email protected]>
Acked-by Kees Cook <[email protected]>
Signed-off-by Zefan Li <[email protected]>
--- include/linux/sched.h | 21 ++++++++++++--------- scripts/tags.sh | 6 ++++++ 2 files changed, 18 insertions(+), 9 deletions(-)
include/linux/sched.h +12 -9
@@ -1959,15 +1959,18 @@ static inline void memalloc_noio_restore(unsigned int flags)/* Per-process atomic flags. */ #define PFA_NO_NEW_PRIVS 0/* May not gain new privileges. */ -static inline bool task_no_new_privs (struct task_struct *p) -{ -return test_bit (PFA_NO_NEW_PRIVS , &p->atomic_flags); -} - -static inline void task_set_no_new_privs (struct task_struct *p) -{ -set_bit (PFA_NO_NEW_PRIVS , &p->atomic_flags); -} +#define TASK_PFA_TEST (name, func) \ + static inline bool task_##func(struct task_struct *p) \ + { return test_bit(PFA_##name, &p->atomic_flags); } +#define TASK_PFA_SET (name, func) \ + static inline void task_set_##func(struct task_struct *p) \ + { set_bit(PFA_##name, &p->atomic_flags); } +#define TASK_PFA_CLEAR (name, func) \ + static inline void task_clear_##func(struct task_struct *p) \ + { clear_bit(PFA_##name, &p->atomic_flags); } + +TASK_PFA_TEST(NO_NEW_PRIVS, no_new_privs) +TASK_PFA_SET (NO_NEW_PRIVS , no_new_privs)/* * task->jobctl flags
scripts/tags.sh +6 -0
@@ -197,6 +197,9 @@ exuberant() --regex-c++='/SETPCGFLAG\(([^,)]*).*/SetPageCgroup\1/' \ --regex-c++='/CLEARPCGFLAG\(([^,)]*).*/ClearPageCgroup\1/' \ --regex-c++='/TESTCLEARPCGFLAG\(([^,)]*).*/TestClearPageCgroup\1/' \ + --regex-c++='/TASK_PFA_TEST\([^,]*,\s*([^)]*)\)/task_\1/' \ + --regex-c++='/TASK_PFA_SET\([^,]*,\s*([^)]*)\)/task_set_\1/' \ + --regex-c++='/TASK_PFA_CLEAR\([^,]*,\s*([^)]*)\)/task_clear_\1/'\ --regex-c='/PCI_OP_READ\((\w*).*[1-4]\)/pci_bus_read_config_\1/' \ --regex-c='/PCI_OP_WRITE\((\w*).*[1-4]\)/pci_bus_write_config_\1/' \ --regex-c='/DEFINE_(MUTEX|SEMAPHORE|SPINLOCK)\((\w*)/\2/v/' \
@@ -260,6 +263,9 @@ emacs() --regex='/SETPCGFLAG\(([^,)]*).*/SetPageCgroup\1/' \ --regex='/CLEARPCGFLAG\(([^,)]*).*/ClearPageCgroup\1/' \ --regex='/TESTCLEARPCGFLAG\(([^,)]*).*/TestClearPageCgroup\1/' \ + --regex='/TASK_PFA_TEST\([^,]*,\s*([^)]*)\)/task_\1/' \ + --regex='/TASK_PFA_SET\([^,]*,\s*([^)]*)\)/task_set_\1/' \ + --regex='/TASK_PFA_CLEAR\([^,]*,\s*([^)]*)\)/task_clear_\1/' \ --regex='/_PE(\([^,)]*\).*/PEVENT_ERRNO__\1/' \ --regex='/PCI_OP_READ(\([a-z]*[a-z]\).*[1-4])/pci_bus_read_config_\1/' \ --regex='/PCI_OP_WRITE(\([a-z]*[a-z]\).*[1-4])/pci_bus_write_config_\1/'\
Signature · 1 line
1.8.0.2
PATCH v4 3/3 cpuset: PF_SPREAD_PAGE and PF_SPREAD_SLAB should be atomic flags
In reply to Zefan LiWhen 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 <[email protected]>
Cc Ingo Molnar <[email protected]>
Cc Miao Xie <[email protected]>
Cc Kees Cook <[email protected]>
Fixes 950592f7b991 ("cpusets: update tasks' page/slab spread flags in time")
Cc <[email protected]> # 2.6.31+
Signed-off-by Zefan Li <[email protected]>
--- Documentation/cgroups/cpusets.txt | 6 +++--- include/linux/cpuset.h | 4 ++-- include/linux/sched.h | 13 +++++++++++-- kernel/cpuset.c | 9 +++++---- mm/slab.c | 4 ++-- 5 files changed, 23 insertions(+), 13 deletions(-)
Documentation/cgroups/cpusets.txt +3 -3
@@ -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
include/linux/cpuset.h +2 -2
@@ -94,12 +94,12 @@ 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 );
include/linux/sched.h +11 -2
@@ -1903,8 +1903,6 @@ extern void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut,#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_NO_SETAFFINITY 0x04000000/* Userland is not allowed to meddle with cpus_allowed */ #define PF_MCE_EARLY 0x08000000/* Early kill for mce process policy */ #define PF_MUTEX_TESTER 0x20000000/* Thread belongs to the rt mutex tester */
@@ -1958,6 +1956,9 @@ static inline void memalloc_noio_restore(unsigned int flags)/* Per-process atomic flags. */ #define PFA_NO_NEW_PRIVS 0/* May not gain new privileges. */ +#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) \
@@ -1972,6 +1973,14 @@ static inline void memalloc_noio_restore(unsigned int flags) TASK_PFA_TEST(NO_NEW_PRIVS, no_new_privs) TASK_PFA_SET(NO_NEW_PRIVS, no_new_privs) +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) +/* * task->jobctl flags */
kernel/cpuset.c +5 -4
@@ -365,13 +365,14 @@ 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); }/*
mm/slab.c +2 -2
@@ -2994,7 +2994,7 @@ out:#ifdef CONFIG_NUMA /* -* Try allocating on another node if PF_SPREAD_SLAB is a mempolicy is set. +* Try allocating on another node if PFA_SPREAD_SLAB is a mempolicy is set. * * If we are in_interrupt, then process context, including cpusets and * mempolicy, may not apply and should not be used for allocation policy.
@@ -3226,7 +3226,7 @@ __do_cache_alloc(struct kmem_cache *cache, gfp_t flags) {void *objp; -if (current->mempolicy ||unlikely (current->flags &PF_SPREAD_SLAB )) { +if (current->mempolicy ||cpuset_do_slab_mem_spread ()) { objp =alternate_node_alloc (cache, flags);if (objp) goto out;
Signature · 1 line
1.8.0.2
Quoted 6 lines · Zefan Li
Commit
1d4457f99928("sched: moveno_new_privsinto new atomic flags") definedPFA_NO_NEW_PRIVSas hexadecimal value, but it is confusing because it is used as bit number. Redefine it as decimal bit number.Note this changes the bit position of
PFA_NOW_NEW_PRIVSfrom 1 to 0.
Quoted 7 lines
Cc Peter Zijlstra <[email protected]>Cc Ingo Molnar <[email protected]>Cc Miao Xie <[email protected]>Signed-off-by Tetsuo Handa <penguin-kernel-JPay3/[email protected]>Acked-by Kees Cook <[email protected]>[ lizf: slightly modified subject and changelog ]Signed-off-by Zefan Li <[email protected]>
Applied to cgroup/for-3.17-fixes.
Thanks.
Signature · 1 line
tejun