The branch main has been updated by kib:
URL:
https://cgit.FreeBSD.org/src/commit/?id=4a69fc16a583face922319c476f3e739d9ce9140
commit 4a69fc16a583face922319c476f3e739d9ce9140
Author: Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2021-10-07 21:10:07 +0000
Commit: Konstantin Belousov <k...@freebsd.org>
CommitDate: 2023-08-23 00:02:21 +0000
Add membarrier(2)
This is an attempt at clean-room implementation of the Linux'
membarrier(2) syscall. For documentation, you would need to read
both membarrier(2) Linux man page, the comments in Linux
kernel/sched/membarrier.c implementation and possibly look at
actual uses.
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D32360
---
lib/libc/sys/Symbol.map | 1 +
sys/conf/files | 1 +
sys/kern/kern_exec.c | 2 +
sys/kern/kern_membarrier.c | 239 +++++++++++++++++++++++++++++++++++++++++++++
sys/kern/syscalls.master | 9 +-
sys/sys/membarrier.h | 70 +++++++++++++
sys/sys/proc.h | 6 ++
sys/sys/syscallsubr.h | 2 +
8 files changed, 329 insertions(+), 1 deletion(-)
diff --git a/lib/libc/sys/Symbol.map b/lib/libc/sys/Symbol.map
index c09c3696c17b..9a07bb457eb8 100644
--- a/lib/libc/sys/Symbol.map
+++ b/lib/libc/sys/Symbol.map
@@ -419,6 +419,7 @@ FBSD_1.7 {
_Fork;
fspacectl;
kqueuex;
+ membarrier;
swapoff;
};
diff --git a/sys/conf/files b/sys/conf/files
index b5cd85cba0e4..3f79ce752c80 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -3780,6 +3780,7 @@ kern/kern_lockstat.c optional kdtrace_hooks
kern/kern_loginclass.c standard
kern/kern_malloc.c standard
kern/kern_mbuf.c standard
+kern/kern_membarrier.c standard
kern/kern_mib.c standard
kern/kern_module.c standard
kern/kern_mtxpool.c standard
diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index 6b0798921da2..ae2b624c2659 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -805,6 +805,8 @@ interpret:
p->p_flag2 &= ~P2_NOTRACE;
if ((p->p_flag2 & P2_STKGAP_DISABLE_EXEC) == 0)
p->p_flag2 &= ~P2_STKGAP_DISABLE;
+ p->p_flag2 &= ~(P2_MEMBAR_PRIVE | P2_MEMBAR_PRIVE_SYNCORE |
+ P2_MEMBAR_GLOBE);
if (p->p_flag & P_PPWAIT) {
p->p_flag &= ~(P_PPWAIT | P_PPTRACE);
cv_broadcast(&p->p_pwait);
diff --git a/sys/kern/kern_membarrier.c b/sys/kern/kern_membarrier.c
new file mode 100644
index 000000000000..eabd00e8ddf4
--- /dev/null
+++ b/sys/kern/kern_membarrier.c
@@ -0,0 +1,239 @@
+/*-
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were developed by Konstantin Belousov <k...@freebsd.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/cpuset.h>
+#include <sys/lock.h>
+#include <sys/membarrier.h>
+#include <sys/mutex.h>
+#include <sys/proc.h>
+#include <sys/sched.h>
+#include <sys/smp.h>
+#include <sys/syscallsubr.h>
+#include <sys/sysproto.h>
+
+#include <vm/vm_param.h>
+#include <vm/vm.h>
+#include <vm/pmap.h>
+#include <vm/vm_map.h>
+
+#define MEMBARRIER_SUPPORTED_CMDS ( \
+ MEMBARRIER_CMD_GLOBAL | \
+ MEMBARRIER_CMD_GLOBAL_EXPEDITED | \
+ MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED | \
+ MEMBARRIER_CMD_PRIVATE_EXPEDITED | \
+ MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED | \
+ MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE | \
+ MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE)
+
+static void
+membarrier_action_seqcst(void *arg __unused)
+{
+ atomic_thread_fence_seq_cst();
+}
+
+static void
+membarrier_action_seqcst_sync_core(void *arg __unused)
+{
+ atomic_thread_fence_seq_cst();
+ cpu_sync_core();
+}
+
+static void
+do_membarrier_ipi(cpuset_t *csp, void (*func)(void *))
+{
+ atomic_thread_fence_seq_cst();
+ smp_rendezvous_cpus(*csp, smp_no_rendezvous_barrier, func,
+ smp_no_rendezvous_barrier, NULL);
+ atomic_thread_fence_seq_cst();
+}
+
+static void
+check_cpu_switched(int c, cpuset_t *csp, uint64_t *swt, bool init)
+{
+ struct pcpu *pc;
+ uint64_t sw;
+
+ if (CPU_ISSET(c, csp))
+ return;
+
+ pc = cpuid_to_pcpu[c];
+ if (pc->pc_curthread == pc->pc_idlethread) {
+ CPU_SET(c, csp);
+ return;
+ }
+
+ /*
+ * Sync with context switch to ensure that override of
+ * pc_curthread with non-idle thread pointer is visible before
+ * reading of pc_switchtime.
+ */
+ atomic_thread_fence_acq();
+
+ sw = pc->pc_switchtime;
+ if (init)
+ swt[c] = sw;
+ else if (sw != swt[c])
+ CPU_SET(c, csp);
+}
+
+/*
+ *
+ * XXXKIB: We execute the requested action (seq_cst and possibly
+ * sync_core) on current CPU as well. There is no guarantee that
+ * current thread executes anything with the full fence semantics
+ * during syscall execution. Similarly, cpu_core_sync() semantics
+ * might be not provided by the syscall return. E.g. on amd64 we
+ * typically return without IRET.
+ */
+int
+kern_membarrier(struct thread *td, int cmd, unsigned flags, int cpu_id)
+{
+ struct proc *p, *p1;
+ struct thread *td1;
+ cpuset_t cs;
+ uint64_t *swt;
+ int c, error;
+ bool first;
+
+ if (flags != 0 || (cmd & ~MEMBARRIER_SUPPORTED_CMDS) != 0)
+ return (EINVAL);
+
+ if (cmd == MEMBARRIER_CMD_QUERY) {
+ td->td_retval[0] = MEMBARRIER_SUPPORTED_CMDS;
+ return (0);
+ }
+
+ p = td->td_proc;
+ error = 0;
+
+ switch (cmd) {
+ case MEMBARRIER_CMD_GLOBAL:
+ swt = malloc((mp_maxid + 1) * sizeof(*swt), M_TEMP, M_WAITOK);
+ CPU_ZERO(&cs);
+ sched_pin();
+ CPU_SET(PCPU_GET(cpuid), &cs);
+ for (first = true; error == 0; first = false) {
+ CPU_FOREACH(c)
+ check_cpu_switched(c, &cs, swt, first);
+ if (CPU_CMP(&cs, &all_cpus) == 0)
+ break;
+ error = pause_sig("mmbr", 1);
+ if (error == EWOULDBLOCK)
+ error = 0;
+ }
+ sched_unpin();
+ free(swt, M_TEMP);
+ atomic_thread_fence_seq_cst();
+ break;
+
+ case MEMBARRIER_CMD_GLOBAL_EXPEDITED:
+ if ((td->td_proc->p_flag2 & P2_MEMBAR_GLOBE) == 0) {
+ error = EPERM;
+ } else {
+ CPU_ZERO(&cs);
+ CPU_FOREACH(c) {
+ td1 = cpuid_to_pcpu[c]->pc_curthread;
+ p1 = td1->td_proc;
+ if (p1 != NULL &&
+ (p1->p_flag2 & P2_MEMBAR_GLOBE) != 0)
+ CPU_SET(c, &cs);
+ }
+ do_membarrier_ipi(&cs, membarrier_action_seqcst);
+ }
+ break;
+
+ case MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED:
+ if ((p->p_flag2 & P2_MEMBAR_GLOBE) == 0) {
+ PROC_LOCK(p);
+ p->p_flag2 |= P2_MEMBAR_GLOBE;
+ PROC_UNLOCK(p);
+ }
+ break;
+
+ case MEMBARRIER_CMD_PRIVATE_EXPEDITED:
+ if ((td->td_proc->p_flag2 & P2_MEMBAR_PRIVE) == 0) {
+ error = EPERM;
+ } else {
+ pmap_active_cpus(vmspace_pmap(p->p_vmspace), &cs);
+ do_membarrier_ipi(&cs, membarrier_action_seqcst);
+ }
+ break;
+
+ case MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED:
+ if ((p->p_flag2 & P2_MEMBAR_PRIVE) == 0) {
+ PROC_LOCK(p);
+ p->p_flag2 |= P2_MEMBAR_PRIVE;
+ PROC_UNLOCK(p);
+ }
+ break;
+
+ case MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE:
+ if ((td->td_proc->p_flag2 & P2_MEMBAR_PRIVE_SYNCORE) == 0) {
+ error = EPERM;
+ } else {
+ /*
+ * Calculating the IPI multicast mask from
+ * pmap active mask means that we do not call
+ * cpu_sync_core() on CPUs that were missed
+ * from pmap active mask but could be switched
+ * from or to meantime. This is fine at least
+ * on amd64 because threads always use slow
+ * (IRETQ) path to return from syscall after
+ * context switch.
+ */
+ pmap_active_cpus(vmspace_pmap(p->p_vmspace), &cs);
+
+ do_membarrier_ipi(&cs,
+ membarrier_action_seqcst_sync_core);
+ }
+ break;
+
+ case MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE:
+ if ((p->p_flag2 & P2_MEMBAR_PRIVE_SYNCORE) == 0) {
+ PROC_LOCK(p);
+ p->p_flag2 |= P2_MEMBAR_PRIVE_SYNCORE;
+ PROC_UNLOCK(p);
+ }
+ break;
+
+ default:
+ error = EINVAL;
+ break;
+ }
+
+ return (error);
+}
+
+int
+sys_membarrier(struct thread *td, struct membarrier_args *uap)
+{
+ return (kern_membarrier(td, uap->cmd, uap->flags, uap->cpu_id));
+}
diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
index 209c3c2fd6db..158ea7036d50 100644
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -3300,7 +3300,6 @@
581 AUE_NULL STD|CAPENABLED {
int sched_getcpu(void);
}
-
582 AUE_SWAPOFF STD {
int swapoff(
_In_z_ const char *name,
@@ -3312,5 +3311,13 @@
u_int flags
);
}
+584 AUE_NULL STD|CAPENABLED {
+ int membarrier(
+ int cmd,
+ unsigned flags,
+ int cpu_id
+ );
+ }
+
; vim: syntax=off
diff --git a/sys/sys/membarrier.h b/sys/sys/membarrier.h
new file mode 100644
index 000000000000..958b769da23e
--- /dev/null
+++ b/sys/sys/membarrier.h
@@ -0,0 +1,70 @@
+/*-
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were developed by Konstantin Belousov <k...@freebsd.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef __SYS_MEMBARRIER_H__
+#define __SYS_MEMBARRIER_H__
+
+#include <sys/cdefs.h>
+
+/*
+ * The enum membarrier_cmd values are bits. The MEMBARRIER_CMD_QUERY
+ * command returns a bitset indicating which commands are supported.
+ * Also the value of MEMBARRIER_CMD_QUERY is zero, so it is
+ * effectively not returned by the query.
+ */
+enum membarrier_cmd {
+ MEMBARRIER_CMD_QUERY = 0x00000000,
+ MEMBARRIER_CMD_GLOBAL = 0x00000001,
+ MEMBARRIER_CMD_SHARED = MEMBARRIER_CMD_GLOBAL,
+ MEMBARRIER_CMD_GLOBAL_EXPEDITED = 0x00000002,
+ MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED = 0x00000004,
+ MEMBARRIER_CMD_PRIVATE_EXPEDITED = 0x00000008,
+ MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = 0x00000010,
+ MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE = 0x00000020,
+ MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE = 0x00000040,
+
+ /*
+ * RSEQ constants are defined for source compatibility but are
+ * not yes supported, MEMBARRIER_CMD_QUERY does not return
+ * them in the mask.
+ */
+ MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ = 0x00000080,
+ MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ = 0x00000100,
+};
+
+enum membarrier_cmd_flag {
+ MEMBARRIER_CMD_FLAG_CPU = 0x00000001,
+};
+
+#ifndef _KERNEL
+__BEGIN_DECLS
+int membarrier(int, unsigned, int);
+__END_DECLS
+#endif /* _KERNEL */
+
+#endif /* __SYS_MEMBARRIER_H__ */
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 05ab914af409..3102cae7add0 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -883,6 +883,12 @@ struct proc {
external thread_single() is
permitted */
#define P2_REAPKILLED 0x00080000
+#define P2_MEMBAR_PRIVE 0x00100000 /* membar private
expedited
+ registered */
+#define P2_MEMBAR_PRIVE_SYNCORE 0x00200000 /* membar private
expedited
+ sync core registered */
+#define P2_MEMBAR_GLOBE 0x00400000 /* membar global
expedited
+ registered */
/* Flags protected by proctree_lock, kept in p_treeflags. */
#define P_TREE_ORPHANED 0x00000001 /* Reparented, on
orphan list */
diff --git a/sys/sys/syscallsubr.h b/sys/sys/syscallsubr.h
index 62cda6d03fd4..8be860dc0fd4 100644
--- a/sys/sys/syscallsubr.h
+++ b/sys/sys/syscallsubr.h
@@ -204,6 +204,8 @@ int kern_minherit(struct thread *td, uintptr_t addr, size_t
len,
int inherit);
int kern_mkdirat(struct thread *td, int fd, const char *path,
enum uio_seg segflg, int mode);
+int kern_membarrier(struct thread *td, int cmd, unsigned flags,
+ int cpu_id);
int kern_mkfifoat(struct thread *td, int fd, const char *path,
enum uio_seg pathseg, int mode);
int kern_mknodat(struct thread *td, int fd, const char *path,
