[tip: sched/core] sched/membarrier: Introduce MEMBARRIER_CMD_GET_REGISTRATIONS

From: tip-bot2 for Michal Clapinski
Date: Sat Jan 07 2023 - 05:53:44 EST


The following commit has been merged into the sched/core branch of tip:

Commit-ID: 544a4f2ecd45f9d6ed78d207583f39130ad40349
Gitweb: https://git.kernel.org/tip/544a4f2ecd45f9d6ed78d207583f39130ad40349
Author: Michal Clapinski <mclapinski@xxxxxxxxxx>
AuthorDate: Wed, 07 Dec 2022 17:43:37 +01:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Sat, 07 Jan 2023 11:29:29 +01:00

sched/membarrier: Introduce MEMBARRIER_CMD_GET_REGISTRATIONS

Provide a method to query previously issued registrations.

Signed-off-by: Michal Clapinski <mclapinski@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221207164338.1535591-2-mclapinski@xxxxxxxxxx
---
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 7376058..5f3ad6d 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 0c5be7e..2ad881d 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;
}