diff --git a/src/LogLock.cpp b/src/LogLock.cpp
index 7f3198d..381c58d 100644
--- a/src/LogLock.cpp
+++ b/src/LogLock.cpp
@@ -9,6 +9,10 @@
 // ESP_LOGx/log_x call to the ESP Insights hook in libesp_diagnostics, and that
 // hook prints through log_printfv().  platformio.ini adds
 // -Wl,--wrap=log_printfv so that call lands here and takes this lock.
+//
+// The lock is a binary semaphore, not a mutex.  A mutex passes its waiter's
+// priority to the holder, so async_tcp waiting on loop() would lift loop()
+// above the radio task and let it break into a frame on the air.
 #include <Arduino.h>
 #include <stdarg.h>
 #include "freertos/FreeRTOS.h"
@@ -17,18 +21,31 @@
 
 extern "C" int __real_log_printfv(const char *format, va_list arg);
 
+static SemaphoreHandle_t createLogLock() {
+  SemaphoreHandle_t sem = xSemaphoreCreateBinary();
+  if(sem) xSemaphoreGive(sem);
+  return sem;
+}
 // Created during static initialisation, before anything can race for it.  A
 // constructor that logs before this runs simply goes unlocked.
-static SemaphoreHandle_t logMutex = xSemaphoreCreateRecursiveMutex();
+static SemaphoreHandle_t logLock = createLogLock();
+// The task holding the lock, so a log from inside a log doesn't wait on itself.
+static volatile TaskHandle_t logOwner = nullptr;
 // Never wait longer than this for the lock; the line is printed anyway, so a
-// task stuck mid-log can only garble output, not hang another task.
-#define LOG_LOCK_WAIT_MS 50
+// task stuck mid-log can only garble output, not hang another task.  A long
+// line takes about 20ms at 115200 baud.
+#define LOG_LOCK_WAIT_MS 20
 
 extern "C" int __wrap_log_printfv(const char *format, va_list arg) {
   // No blocking before the scheduler runs, in an ISR or in a critical section.
-  const bool canLock = logMutex && xTaskGetSchedulerState() == taskSCHEDULER_RUNNING && xPortCanYield();
-  const bool locked = canLock && xSemaphoreTakeRecursive(logMutex, pdMS_TO_TICKS(LOG_LOCK_WAIT_MS)) == pdTRUE;
+  const bool canLock = logLock && xTaskGetSchedulerState() == taskSCHEDULER_RUNNING && xPortCanYield() &&
+    logOwner != xTaskGetCurrentTaskHandle();
+  const bool locked = canLock && xSemaphoreTake(logLock, pdMS_TO_TICKS(LOG_LOCK_WAIT_MS)) == pdTRUE;
+  if(locked) logOwner = xTaskGetCurrentTaskHandle();
   int len = __real_log_printfv(format, arg);
-  if(locked) xSemaphoreGiveRecursive(logMutex);
+  if(locked) {
+    logOwner = nullptr;
+    xSemaphoreGive(logLock);
+  }
   return len;
 }