tty: hvc: hvc_poll() may sleep

Introduce points where hvc_poll drops the lock, enables interrupts,
and reschedules.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 745ac22..2abfc0b 100644 (file)
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -589,7 +589,7 @@ static u32 timeout = MIN_TIMEOUT;
 #define HVC_POLL_READ  0x00000001
 #define HVC_POLL_WRITE 0x00000002
 
-int hvc_poll(struct hvc_struct *hp)
+static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
 {
        struct tty_struct *tty;
        int i, n, count, poll_mask = 0;
@@ -611,6 +611,12 @@ int hvc_poll(struct hvc_struct *hp)
                timeout = (written_total) ? 0 : MIN_TIMEOUT;
        }
 
+       if (may_sleep) {
+               spin_unlock_irqrestore(&hp->lock, flags);
+               cond_resched();
+               spin_lock_irqsave(&hp->lock, flags);
+       }
+
        /* No tty attached, just skip */
        tty = tty_port_tty_get(&hp->port);
        if (tty == NULL)
@@ -698,6 +704,11 @@ int hvc_poll(struct hvc_struct *hp)
 
        return poll_mask;
 }
+
+int hvc_poll(struct hvc_struct *hp)
+{
+       return __hvc_poll(hp, false);
+}
 EXPORT_SYMBOL_GPL(hvc_poll);
 
 /**
@@ -736,7 +747,8 @@ static int khvcd(void *unused)
                if (!cpus_are_in_xmon()) {
                        mutex_lock(&hvc_structs_mutex);
                        list_for_each_entry(hp, &hvc_structs, next) {
-                               poll_mask |= hvc_poll(hp);
+                               poll_mask |= __hvc_poll(hp, true);
+                               cond_resched();
                        }
                        mutex_unlock(&hvc_structs_mutex);
                } else