[nrf toup][nrfconnect] Retry BLE advertising restart

Replace the sWasDisconnection flag with an atomic restart flag so
advertising can be retried when bt_le_adv_start() fails due to lack
of available connection object.

With CONFIG_CHIP_BLE_MULTI_IDENTITY_SUPPORT, disconnect and recycled
callbacks can arrive in an order where a restart attempt runs before
all connection slots are available. Re-arm the flag on failure so a
subsequent recycled callback schedules another restart attempt.

Signed-off-by: Adrian Gielniewski <adrian.gielniewski@nordicsemi.no>
(cherry picked from commit 6d8ea97)

Author: adigie

src/platform/Zephyr/BLEAdvertisingArbiter.cpp

@@ -31,9 +31,9 @@ namespace {
 // List of advertising requests ordered by priority
 sys_slist_t sRequests;
 
-bool sIsInitialized    = false;
-bool sWasDisconnection = false;
-uint8_t sBtId          = 0;
+bool sIsInitialized = false;
+atomic_t sRestart   = ATOMIC_INIT(0);
+uint8_t sBtId       = 0;
 
 // Cast an intrusive list node to the containing request object
 const BLEAdvertisingArbiter::Request & ToRequest(const sys_snode_t * node)
@@ -103,25 +103,32 @@ BT_CONN_CB_DEFINE(conn_callbacks) = {
             // Ignore disconnections from other identities
             VerifyOrReturn(IsOurIdentity(conn));
 #endif // CONFIG_CHIP_BLE_MULTI_IDENTITY_SUPPORT
-            sWasDisconnection = true;
+            atomic_set(&sRestart, 1);
         },
     .recycled =
         []() {
             // In this callback the connection object was returned to the pool and we can try to re-start connectable
-            // advertising, but only if the disconnection was detected.
-            if (sWasDisconnection)
+            // advertising, but only if the disconnection was detected or a previous restart attempt failed.
+            constexpr atomic_val_t oldValue = 1;
+            constexpr atomic_val_t newValue = 0;
+            const bool shouldRestart        = atomic_cas(&sRestart, oldValue, newValue);
+
+            if (shouldRestart)
             {
+
                 SystemLayer().ScheduleLambda([] {
                     if (!sys_slist_is_empty(&sRequests))
                     {
                         // Starting from Zephyr 4.0 Automatic advertiser resumption is deprecated,
                         // so the BLE Advertising Arbiter has to take over the responsibility of restarting the advertiser.
                         // Restart advertising in this callback if there are pending requests after the connection is released.
-                        RestartAdvertising();
+                        const CHIP_ERROR result = RestartAdvertising();
+                        if (result != CHIP_NO_ERROR)
+                        {
+                            atomic_set(&sRestart, 1);
+                        }
                     }
                 });
-                // Reset the disconnection flag to avoid restarting advertising multiple times
-                sWasDisconnection = false;
             }
         },
 };