Merge branch 'depends/tty' into next/headers

Merging in Greg's tty tree including a cleanup patch needed by the OMAP serial
header cleanups.

* depends/tty: (305 commits)
  tty/serial/8250: Make omap hardware workarounds local to 8250.h
  serial/8250/8250_early: Prevent rounding error in uartclk
  serial: samsung: use clk_prepare_enable and clk_disable_unprepare
  TTY: Report warning when low_latency flag is wrongly used
  console: use might_sleep in console_lock
  TTY: move tty buffers to tty_port
  TTY: add port -> tty link
  TTY: tty_buffer, cache pointer to tty->buf
  TTY: move TTY_FLUSH* flags to tty_port
  TTY: n_tty, propagate n_tty_data
  TTY: move ldisc data from tty_struct: locks
  TTY: move ldisc data from tty_struct: read_* and echo_* and canon_* stuff
  TTY: move ldisc data from tty_struct: bitmaps
  TTY: move ldisc data from tty_struct: simple members
  TTY: n_tty, add ldisc data to n_tty
  TTY: audit, stop accessing tty->icount
  TTY: n_tty, remove bogus checks
  TTY: n_tty, simplify read_buf+echo_buf allocation
  TTY: hci_ldisc, remove invalid check in open
  TTY: ldisc, wait for idle ldisc in release
  ...

1 files changed, 50 insertions, 3 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 79827ce03e3b..90c63f9392a5 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -90,10 +90,55 @@ static void pad_len_spaces(struct seq_file *m, int len)
 	seq_printf(m, "%*c", len, ' ');
 }
 
+#ifdef CONFIG_NUMA
+/*
+ * These functions are for numa_maps but called in generic **maps seq_file
+ * ->start(), ->stop() ops.
+ *
+ * numa_maps scans all vmas under mmap_sem and checks their mempolicy.
+ * Each mempolicy object is controlled by reference counting. The problem here
+ * is how to avoid accessing dead mempolicy object.
+ *
+ * Because we're holding mmap_sem while reading seq_file, it's safe to access
+ * each vma's mempolicy, no vma objects will never drop refs to mempolicy.
+ *
+ * A task's mempolicy (task->mempolicy) has different behavior. task->mempolicy
+ * is set and replaced under mmap_sem but unrefed and cleared under task_lock().
+ * So, without task_lock(), we cannot trust get_vma_policy() because we cannot
+ * gurantee the task never exits under us. But taking task_lock() around
+ * get_vma_plicy() causes lock order problem.
+ *
+ * To access task->mempolicy without lock, we hold a reference count of an
+ * object pointed by task->mempolicy and remember it. This will guarantee
+ * that task->mempolicy points to an alive object or NULL in numa_maps accesses.
+ */
+static void hold_task_mempolicy(struct proc_maps_private *priv)
+{
+	struct task_struct *task = priv->task;
+
+	task_lock(task);
+	priv->task_mempolicy = task->mempolicy;
+	mpol_get(priv->task_mempolicy);
+	task_unlock(task);
+}
+static void release_task_mempolicy(struct proc_maps_private *priv)
+{
+	mpol_put(priv->task_mempolicy);
+}
+#else
+static void hold_task_mempolicy(struct proc_maps_private *priv)
+{
+}
+static void release_task_mempolicy(struct proc_maps_private *priv)
+{
+}
+#endif
+
 static void vma_stop(struct proc_maps_private *priv, struct vm_area_struct *vma)
 {
 	if (vma && vma != priv->tail_vma) {
 		struct mm_struct *mm = vma->vm_mm;
+		release_task_mempolicy(priv);
 		up_read(&mm->mmap_sem);
 		mmput(mm);
 	}
@@ -132,7 +177,7 @@ static void *m_start(struct seq_file *m, loff_t *pos)
 
 	tail_vma = get_gate_vma(priv->task->mm);
 	priv->tail_vma = tail_vma;
-
+	hold_task_mempolicy(priv);
 	/* Start with last addr hint */
 	vma = find_vma(mm, last_addr);
 	if (last_addr && vma) {
@@ -159,6 +204,7 @@ out:
 	if (vma)
 		return vma;
 
+	release_task_mempolicy(priv);
 	/* End of vmas has been reached */
 	m->version = (tail_vma != NULL)? 0: -1UL;
 	up_read(&mm->mmap_sem);
@@ -1158,6 +1204,7 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
 	struct vm_area_struct *vma = v;
 	struct numa_maps *md = &numa_priv->md;
 	struct file *file = vma->vm_file;
+	struct task_struct *task = proc_priv->task;
 	struct mm_struct *mm = vma->vm_mm;
 	struct mm_walk walk = {};
 	struct mempolicy *pol;
@@ -1177,7 +1224,7 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
 	walk.private = md;
 	walk.mm = mm;
 
-	pol = get_vma_policy(proc_priv->task, vma, vma->vm_start);
+	pol = get_vma_policy(task, vma, vma->vm_start);
 	mpol_to_str(buffer, sizeof(buffer), pol, 0);
 	mpol_cond_put(pol);
 
@@ -1189,7 +1236,7 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
 	} else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
 		seq_printf(m, " heap");
 	} else {
-		pid_t tid = vm_is_stack(proc_priv->task, vma, is_pid);
+		pid_t tid = vm_is_stack(task, vma, is_pid);
 		if (tid != 0) {
 			/*
 			 * Thread stack in /proc/PID/task/TID/maps or