Provide a method to query previously issued registrations.
Signed-off-by: Michal Clapinski mclapinski@google.com --- include/uapi/linux/membarrier.h | 4 ++++ kernel/sched/membarrier.c | 39 ++++++++++++++++++++++++++++++++- 2 files changed, 42 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/membarrier.h b/include/uapi/linux/membarrier.h index 737605897f36..5f3ad6d5be6f 100644 --- a/include/uapi/linux/membarrier.h +++ b/include/uapi/linux/membarrier.h @@ -137,6 +137,9 @@ * @MEMBARRIER_CMD_SHARED: * Alias to MEMBARRIER_CMD_GLOBAL. Provided for * header backward compatibility. + * @MEMBARRIER_CMD_GET_REGISTRATIONS: + * Returns a bitmask of previously issued + * registration commands. * * Command to be passed to the membarrier system call. The commands need to * be a single bit each, except for MEMBARRIER_CMD_QUERY which is assigned to @@ -153,6 +156,7 @@ enum membarrier_cmd { MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 6), MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ = (1 << 7), MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ = (1 << 8), + MEMBARRIER_CMD_GET_REGISTRATIONS = (1 << 9),
/* Alias for header backward compatibility. */ MEMBARRIER_CMD_SHARED = MEMBARRIER_CMD_GLOBAL, diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c index 0c5be7ebb1dc..2ad881d07752 100644 --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -159,7 +159,8 @@ | MEMBARRIER_CMD_PRIVATE_EXPEDITED \ | MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED \ | MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK \ - | MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK) + | MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK \ + | MEMBARRIER_CMD_GET_REGISTRATIONS)
static void ipi_mb(void *info) { @@ -540,6 +541,40 @@ static int membarrier_register_private_expedited(int flags) return 0; }
+static int membarrier_get_registrations(void) +{ + struct task_struct *p = current; + struct mm_struct *mm = p->mm; + int registrations_mask = 0, membarrier_state, i; + static const int states[] = { + MEMBARRIER_STATE_GLOBAL_EXPEDITED | + MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY, + MEMBARRIER_STATE_PRIVATE_EXPEDITED | + MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY, + MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE | + MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY, + MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ | + MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ_READY + }; + static const int registration_cmds[] = { + MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED, + MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, + MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE, + MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ + }; + BUILD_BUG_ON(ARRAY_SIZE(states) != ARRAY_SIZE(registration_cmds)); + + membarrier_state = atomic_read(&mm->membarrier_state); + for (i = 0; i < ARRAY_SIZE(states); ++i) { + if (membarrier_state & states[i]) { + registrations_mask |= registration_cmds[i]; + membarrier_state &= ~states[i]; + } + } + WARN_ON_ONCE(membarrier_state != 0); + return registrations_mask; +} + /** * sys_membarrier - issue memory barriers on a set of threads * @cmd: Takes command values defined in enum membarrier_cmd. @@ -623,6 +658,8 @@ SYSCALL_DEFINE3(membarrier, int, cmd, unsigned int, flags, int, cpu_id) return membarrier_private_expedited(MEMBARRIER_FLAG_RSEQ, cpu_id); case MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ: return membarrier_register_private_expedited(MEMBARRIER_FLAG_RSEQ); + case MEMBARRIER_CMD_GET_REGISTRATIONS: + return membarrier_get_registrations(); default: return -EINVAL; }