diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 1c4e40c5efaf5..03a169087a18d 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -7,6 +7,7 @@
#include <linux/sched.h>
#include <linux/mm_types.h>
#include <linux/gfp.h>
+#include <linux/sync_core.h>
/*
* Routines for handling mm_structs
@@ -223,12 +224,26 @@ enum {
MEMBARRIER_STATE_PRIVATE_EXPEDITED = (1U << 1),
MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY = (1U << 2),
MEMBARRIER_STATE_GLOBAL_EXPEDITED = (1U << 3),
+ MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY = (1U << 4),
+ MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE = (1U << 5),
+};
+
+enum {
+ MEMBARRIER_FLAG_SYNC_CORE = (1U << 0),
};
#ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
#include <asm/membarrier.h>
#endif
+static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
+{
+ if (likely(!(atomic_read(&mm->membarrier_state) &
+ MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
+ return;
+ sync_core_before_usermode();
+}
+
static inline void membarrier_execve(struct task_struct *t)
{
atomic_set(&t->mm->membarrier_state, 0);
@@ -244,6 +259,9 @@ static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
static inline void membarrier_execve(struct task_struct *t)
{
}
+static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
+{
+}
#endif
#endif /* _LINUX_SCHED_MM_H */
diff --git a/include/uapi/linux/membarrier.h b/include/uapi/linux/membarrier.h
index d252506e1b5e8..5891d7614c8c0 100644
--- a/include/uapi/linux/membarrier.h
+++ b/include/uapi/linux/membarrier.h
@@ -73,7 +73,7 @@
* to and return from the system call
* (non-running threads are de facto in such a
* state). This only covers threads from the
- * same processes as the caller thread. This
+ * same process as the caller thread. This
* command returns 0 on success. The
* "expedited" commands complete faster than
* the non-expedited ones, they never block,
@@ -86,6 +86,34 @@
* Register the process intent to use
* MEMBARRIER_CMD_PRIVATE_EXPEDITED. Always
* returns 0.
+ * @MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE:
+ * In addition to provide memory ordering
+ * guarantees described in
+ * MEMBARRIER_CMD_PRIVATE_EXPEDITED, ensure
+ * the caller thread, upon return from system
+ * call, that all its running threads siblings
+ * have executed a core serializing
+ * instruction. (architectures are required to
+ * guarantee that non-running threads issue
+ * core serializing instructions before they
+ * resume user-space execution). This only
+ * covers threads from the same process as the
+ * caller thread. This command returns 0 on
+ * success. The "expedited" commands complete
+ * faster than the non-expedited ones, they
+ * never block, but have the downside of
+ * causing extra overhead. If this command is
+ * not implemented by an architecture, -EINVAL
+ * is returned. A process needs to register its
+ * intent to use the private expedited sync
+ * core command prior to using it, otherwise
+ * this command returns -EPERM.
+ * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE:
+ * Register the process intent to use
+ * MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE.
+ * If this command is not implemented by an
+ * architecture, -EINVAL is returned.
+ * Returns 0 on success.
* @MEMBARRIER_CMD_SHARED:
* Alias to MEMBARRIER_CMD_GLOBAL. Provided for
* header backward compatibility.
@@ -101,6 +129,8 @@ enum membarrier_cmd {
MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED = (1 << 2),
MEMBARRIER_CMD_PRIVATE_EXPEDITED = (1 << 3),
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = (1 << 4),
+ MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 5),
+ MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 6),
/* Alias for header backward compatibility. */
MEMBARRIER_CMD_SHARED = MEMBARRIER_CMD_GLOBAL,
diff --git a/init/Kconfig b/init/Kconfig
index 535421facea88..e37f4b2a64453 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1415,6 +1415,9 @@ config USERFAULTFD
config ARCH_HAS_MEMBARRIER_CALLBACKS
bool
+config ARCH_HAS_MEMBARRIER_SYNC_CORE
+ bool
+
config EMBEDDED
bool "Embedded system"
option allnoconfig_y
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 11bf4d48d2d36..ee420d78e674d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2704,13 +2704,21 @@ static struct rq *finish_task_switch(struct task_struct *prev)
fire_sched_in_preempt_notifiers(current);
/*
- * When transitioning from a kernel thread to a userspace
- * thread, mmdrop()'s implicit full barrier is required by the
- * membarrier system call, because the current ->active_mm can
- * become the current mm without going through switch_mm().
+ * When switching through a kernel thread, the loop in
+ * membarrier_{private,global}_expedited() may have observed that
+ * kernel thread and not issued an IPI. It is therefore possible to
+ * schedule between user->kernel->user threads without passing though
+ * switch_mm(). Membarrier requires a barrier after storing to
+ * rq->curr, before returning to userspace, so provide them here:
+ *
+ * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
+ * provided by mmdrop(),
+ * - a sync_core for SYNC_CORE.
*/
- if (mm)
+ if (mm) {
+ membarrier_mm_sync_core_before_usermode(mm);
mmdrop(mm);
+ }
if (unlikely(prev_state == TASK_DEAD)) {
if (prev->sched_class->task_dead)
prev->sched_class->task_dead(prev);
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index d2087d5f98376..5d07626336397 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -26,11 +26,20 @@
* Bitmask made from a "or" of all commands within enum membarrier_cmd,
* except MEMBARRIER_CMD_QUERY.
*/
+#ifdef CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE
+#define MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK \
+ (MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE \
+ | MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE)
+#else
+#define MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK 0
+#endif
+
#define MEMBARRIER_CMD_BITMASK \
(MEMBARRIER_CMD_GLOBAL | MEMBARRIER_CMD_GLOBAL_EXPEDITED \
| MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED \
| MEMBARRIER_CMD_PRIVATE_EXPEDITED \
- | MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED)
+ | MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED \
+ | MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK)
static void ipi_mb(void *info)
{
@@ -104,15 +113,23 @@ static int membarrier_global_expedited(void)
return 0;
}
-static int membarrier_private_expedited(void)
+static int membarrier_private_expedited(int flags)
{
int cpu;
bool fallback = false;
cpumask_var_t tmpmask;
- if (!(atomic_read(¤t->mm->membarrier_state)
- & MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY))
- return -EPERM;
+ if (flags & MEMBARRIER_FLAG_SYNC_CORE) {
+ if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE))
+ return -EINVAL;
+ if (!(atomic_read(¤t->mm->membarrier_state) &
+ MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY))
+ return -EPERM;
+ } else {
+ if (!(atomic_read(¤t->mm->membarrier_state) &
+ MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY))
+ return -EPERM;
+ }
if (num_online_cpus() == 1)
return 0;
@@ -205,20 +222,29 @@ static int membarrier_register_global_expedited(void)
return 0;
}
-static int membarrier_register_private_expedited(void)
+static int membarrier_register_private_expedited(int flags)
{
struct task_struct *p = current;
struct mm_struct *mm = p->mm;
+ int state = MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY;
+
+ if (flags & MEMBARRIER_FLAG_SYNC_CORE) {
+ if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE))
+ return -EINVAL;
+ state = MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY;
+ }
/*
* We need to consider threads belonging to different thread
* groups, which use the same mm. (CLONE_VM but not
* CLONE_THREAD).
*/
- if (atomic_read(&mm->membarrier_state)
- & MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY)
+ if (atomic_read(&mm->membarrier_state) & state)
return 0;
atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED, &mm->membarrier_state);
+ if (flags & MEMBARRIER_FLAG_SYNC_CORE)
+ atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE,
+ &mm->membarrier_state);
if (!(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)) {
/*
* Ensure all future scheduler executions will observe the
@@ -226,8 +252,7 @@ static int membarrier_register_private_expedited(void)
*/
synchronize_sched();
}
- atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY,
- &mm->membarrier_state);
+ atomic_or(state, &mm->membarrier_state);
return 0;
}
@@ -283,9 +308,13 @@ SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
case MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED:
return membarrier_register_global_expedited();
case MEMBARRIER_CMD_PRIVATE_EXPEDITED:
- return membarrier_private_expedited();
+ return membarrier_private_expedited(0);
case MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED:
- return membarrier_register_private_expedited();
+ return membarrier_register_private_expedited(0);
+ case MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE:
+ return membarrier_private_expedited(MEMBARRIER_FLAG_SYNC_CORE);
+ case MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE:
+ return membarrier_register_private_expedited(MEMBARRIER_FLAG_SYNC_CORE);
default:
return -EINVAL;
}