Merge branch 'devx-async' into k.o/for-next

Yishai Hadas says:

Enable DEVX asynchronous query commands

This series enables querying a DEVX object in an asynchronous mode.

The userspace application won't block when calling the firmware and it will be
able to get the response back once that it will be ready.

To enable the above functionality:

- DEVX asynchronous command completion FD object was introduced.
- The applicable file operations were implemented to enable using it by
  the user application.
- Query asynchronous method was added to the DEVX object, it will call the
  firmware asynchronously and manages the response on the given input FD.
- Hot unplug support was added for the FD to work properly upon
  unbind/disassociate.
- mlx5 core fence for asynchronous commands was implemented and used to
  prevent racing upon unbind/disassociate.

This branch is based on mlx5-next & v5.0-rc2 due to dependencies, from
git://git.kernel.org/pub/scm/linux/kernel/git/mellanox/linux

* branch 'devx-async':
  IB/mlx5: Implement DEVX hot unplug for async command FD
  IB/mlx5: Implement the file ops of DEVX async command FD
  IB/mlx5: Introduce async DEVX obj query API
  IB/mlx5: Introduce MLX5_IB_OBJECT_DEVX_ASYNC_CMD_FD

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

2 files changed, 14 insertions, 3 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index a60459947f18..b69248e6f0e0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -217,6 +217,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 		memset(s->addr, 0, THREAD_SIZE);
 
 		tsk->stack_vm_area = s;
+		tsk->stack = s->addr;
 		return s->addr;
 	}
 
@@ -1833,8 +1834,6 @@ static __latent_entropy struct task_struct *copy_process(
 
 	posix_cpu_timers_init(p);
 
-	p->start_time = ktime_get_ns();
-	p->real_start_time = ktime_get_boot_ns();
 	p->io_context = NULL;
 	audit_set_context(p, NULL);
 	cgroup_fork(p);
@@ -2001,6 +2000,17 @@ static __latent_entropy struct task_struct *copy_process(
 		goto bad_fork_free_pid;
 
 	/*
+	 * From this point on we must avoid any synchronous user-space
+	 * communication until we take the tasklist-lock. In particular, we do
+	 * not want user-space to be able to predict the process start-time by
+	 * stalling fork(2) after we recorded the start_time but before it is
+	 * visible to the system.
+	 */
+
+	p->start_time = ktime_get_ns();
+	p->real_start_time = ktime_get_boot_ns();
+
+	/*
 	 * Make it visible to the rest of the system, but dont wake it up yet.
 	 * Need tasklist lock for parent etc handling!
 	 */
diff --git a/kernel/sys.c b/kernel/sys.c
index a48cbf1414b8..f7eb62eceb24 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1207,7 +1207,8 @@ DECLARE_RWSEM(uts_sem);
 /*
  * Work around broken programs that cannot handle "Linux 3.0".
  * Instead we map 3.x to 2.6.40+x, so e.g. 3.0 would be 2.6.40
- * And we map 4.x to 2.6.60+x, so 4.0 would be 2.6.60.
+ * And we map 4.x and later versions to 2.6.60+x, so 4.0/5.0/6.0/... would be
+ * 2.6.60.
  */
 static int override_release(char __user *release, size_t len)
 {