From 54c4a833f9f46462e117e0fe3b48baf1e395138a Mon Sep 17 00:00:00 2001
From: "S. Sivarajah" <sivarajah.sivapiriyan@greenwaves-technologies.com>
Date: Thu, 19 Dec 2019 10:58:53 +0100
Subject: [PATCH 1/2] Add __io_lock() and __io_unlock() functions to lock io
 functions such as printf in order to avoid collision between multiple
 threads/cores.

---
 printf.c |  2 ++
 printf.h | 11 +++++++++++
 2 files changed, 13 insertions(+)

diff --git a/printf.c b/printf.c
index 8a700add..4481911d 100644
--- a/printf.c
+++ b/printf.c
@@ -861,11 +861,13 @@ static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const
 
 int printf_(const char* format, ...)
 {
+  __io_lock();
   va_list va;
   va_start(va, format);
   char buffer[1];
   const int ret = _vsnprintf(_out_char, buffer, (size_t)-1, format, va);
   va_end(va);
+  __io_unlock();
   return ret;
 }
 
diff --git a/printf.h b/printf.h
index 6104ccfb..c8f19241 100644
--- a/printf.h
+++ b/printf.h
@@ -40,6 +40,17 @@
 extern "C" {
 #endif
 
+/**
+ * Lock the printf to avoid collision when multiple threads/cores try to output strings/characters.
+ * This function can implement a mutex, semaphore or whatever lock.
+ */
+void __io_lock();
+
+/**
+ * Unlock the printf, release the lock, semaphore or mutex used to lock printf.
+ * This function releases the mutex, semaphore or whatever lock used previously.
+ */
+void __io_unlock();
 
 /**
  * Output a character to a custom device like UART, used by the printf() function

From 3455e53aea1a46a7b56fa5ddf6394a37e68f63a5 Mon Sep 17 00:00:00 2001
From: "S. Sivarajah" <sivarajah.sivapiriyan@greenwaves-technologies.com>
Date: Thu, 19 Dec 2019 16:21:13 +0100
Subject: [PATCH 2/2] Add flags to enable lock/unlock in printf

---
 printf.c | 10 ++++++++++
 printf.h |  4 ++++
 2 files changed, 14 insertions(+)

diff --git a/printf.c b/printf.c
index 4481911d..fa0f06e9 100644
--- a/printf.c
+++ b/printf.c
@@ -95,6 +95,12 @@
 #define PRINTF_SUPPORT_PTRDIFF_T
 #endif
 
+// add lock and unlock functions to protect io operations
+// default: deactivated
+#ifdef PRINTF_ENABLE_LOCK
+#define PRINTF_IO_LOCK
+#endif
+
 ///////////////////////////////////////////////////////////////////////////////
 
 // internal flag definitions
@@ -861,13 +867,17 @@ static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const
 
 int printf_(const char* format, ...)
 {
+#if defined(PRINTF_IO_LOCK)
   __io_lock();
+#endif
   va_list va;
   va_start(va, format);
   char buffer[1];
   const int ret = _vsnprintf(_out_char, buffer, (size_t)-1, format, va);
   va_end(va);
+#if defined(PRINTF_IO_LOCK)
   __io_unlock();
+#endif
   return ret;
 }
 
diff --git a/printf.h b/printf.h
index c8f19241..6b2cf5c9 100644
--- a/printf.h
+++ b/printf.h
@@ -43,12 +43,16 @@ extern "C" {
 /**
  * Lock the printf to avoid collision when multiple threads/cores try to output strings/characters.
  * This function can implement a mutex, semaphore or whatever lock.
+ *
+ * \note PRINTF_ENABLE_LOCK should be defined in order to activate lock function.
  */
 void __io_lock();
 
 /**
  * Unlock the printf, release the lock, semaphore or mutex used to lock printf.
  * This function releases the mutex, semaphore or whatever lock used previously.
+ *
+ * \note PRINTF_ENABLE_LOCK should be defined in order to activate unlock function.
  */
 void __io_unlock();