Commit 544a4f2e authored by Michal Clapinski's avatar Michal Clapinski Committed by Ingo Molnar
Browse files

sched/membarrier: Introduce MEMBARRIER_CMD_GET_REGISTRATIONS 



Provide a method to query previously issued registrations.

Signed-off-by: default avatarMichal Clapinski <mclapinski@google.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20221207164338.1535591-2-mclapinski@google.com
parent 948fb4c4

include/uapi/linux/membarrier.h

+4 −0
Original line number Diff line number Diff line
@@ -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,

kernel/sched/membarrier.c

+38 −1
Original line number Diff line number Diff line
@@ -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;

	}