w1/masters/ds2490: queue up found IDs during scan

Queue up found IDs in a buffer and run the callback once for each found ID
at the end. This is necessary because we hold the bus_mutex during the
whole scan, and some of the "add-device" callbacks deadlock as they
themselves want to mutex_lock(bus_mutex).

Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Christian Vogel <vogelchr@vogel.cx>
Link: https://lore.kernel.org/r/20210113195018.7498-3-vogelchr@vogel.cx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/w1/masters/ds2490.c b/drivers/w1/masters/ds2490.c
index e17c8f70dcd07e4a3f8f29c28a707c05b8372b35..cd8821580f71628856c3baccbe5ca1a23cf6d1ed 100644 (file)
--- a/drivers/w1/masters/ds2490.c
+++ b/drivers/w1/masters/ds2490.c
@@ -688,12 +688,22 @@ static void ds9490r_search(void *data, struct w1_master *master,
         * packet size.
         */
        const size_t bufsize = 2 * 64;
-       u64 *buf;
+       u64 *buf, *found_ids;
 
        buf = kmalloc(bufsize, GFP_KERNEL);
        if (!buf)
                return;
 
+       /*
+        * We are holding the bus mutex during the scan, but adding devices via the
+        * callback needs the bus to be unlocked. So we queue up found ids here.
+        */
+       found_ids = kmalloc_array(master->max_slave_count, sizeof(u64), GFP_KERNEL);
+       if (!found_ids) {
+               kfree(buf);
+               return;
+       }
+
        mutex_lock(&master->bus_mutex);
 
        /* address to start searching at */
@@ -729,13 +739,13 @@ static void ds9490r_search(void *data, struct w1_master *master,
                        if (err < 0)
                                break;
                        for (i = 0; i < err/8; ++i) {
-                               ++found;
-                               if (found <= search_limit)
-                                       callback(master, buf[i]);
+                               found_ids[found++] = buf[i];
                                /* can't know if there will be a discrepancy
                                 * value after until the next id */
-                               if (found == search_limit)
+                               if (found == search_limit) {
                                        master->search_id = buf[i];
+                                       break;
+                               }
                        }
                }
 
@@ -759,9 +769,14 @@ static void ds9490r_search(void *data, struct w1_master *master,
                        master->max_slave_count);
                set_bit(W1_WARN_MAX_COUNT, &master->flags);
        }
+
 search_out:
        mutex_unlock(&master->bus_mutex);
        kfree(buf);
+
+       for (i = 0; i < found; i++) /* run callback for all queued up IDs */
+               callback(master, found_ids[i]);
+       kfree(found_ids);
 }
 
 #if 0