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sched/membarrier: Introduce MEMBARRIER_CMD_GET_REGISTRATIONS

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Provide a method to query previously issued registrations.

Signed-off-by: Michal Clapinski <mclapinski@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20221207164338.1535591-2-mclapinski@google.com
This commit is contained in:
Michal Clapinski 2022-12-07 17:43:37 +01:00 committed by Ingo Molnar
parent 948fb4c4e9
commit 544a4f2ecd
2 changed files with 42 additions and 1 deletions
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4
include/uapi/linux/membarrier.h
View File

@ -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,

39
kernel/sched/membarrier.c
View File

@ -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;
}