diff --git a/docs/reports/LPC1114-48-GCC.txt b/docs/reports/LPC1114-48-GCC.txt
index 260d994a4..32ea4154e 100644
--- a/docs/reports/LPC1114-48-GCC.txt
+++ b/docs/reports/LPC1114-48-GCC.txt
@@ -5,7 +5,7 @@ Settings: CLK=48, (2 wait states)
 
 *** ChibiOS/RT test suite
 ***
-*** Kernel:       2.1.7unstable
+*** Kernel:       2.3.0unstable
 *** GCC Version:  4.3.3
 *** Architecture: ARMv6-M
 *** Core Variant: Cortex-M0
@@ -98,51 +98,51 @@ Settings: CLK=48, (2 wait states)
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.1 (Benchmark, messages #1)
---- Score : 124135 msgs/S, 248270 ctxswc/S
+--- Score : 126834 msgs/S, 253668 ctxswc/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.2 (Benchmark, messages #2)
---- Score : 99992 msgs/S, 199984 ctxswc/S
+--- Score : 100879 msgs/S, 201758 ctxswc/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.3 (Benchmark, messages #3)
---- Score : 99992 msgs/S, 199984 ctxswc/S
+--- Score : 100879 msgs/S, 201758 ctxswc/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.4 (Benchmark, context switch)
---- Score : 380432 ctxswc/S
+--- Score : 380632 ctxswc/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.5 (Benchmark, threads, full cycle)
---- Score : 78349 threads/S
+--- Score : 78390 threads/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.6 (Benchmark, threads, create only)
---- Score : 110375 threads/S
+--- Score : 110433 threads/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.7 (Benchmark, mass reschedule, 5 threads)
---- Score : 31034 reschedules/S, 186204 ctxswc/S
+--- Score : 31050 reschedules/S, 186300 ctxswc/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.8 (Benchmark, round robin context switching)
---- Score : 253200 ctxswc/S
+--- Score : 253332 ctxswc/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.9 (Benchmark, I/O Queues throughput)
---- Score : 298992 bytes/S
+--- Score : 296368 bytes/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.10 (Benchmark, virtual timers set/reset)
---- Score : 350196 timers/S
+--- Score : 350378 timers/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.11 (Benchmark, semaphores wait/signal)
---- Score : 591948 wait+signal/S
+--- Score : 592280 wait+signal/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.12 (Benchmark, mutexes lock/unlock)
---- Score : 334860 lock+unlock/S
+--- Score : 335036 lock+unlock/S
 --- Result: SUCCESS
 ----------------------------------------------------------------------------
 --- Test Case 11.13 (Benchmark, RAM footprint)
diff --git a/os/ports/GCC/ARMCMx/chcore_v6m.c b/os/ports/GCC/ARMCMx/chcore_v6m.c
index 790761876..4e49e6256 100644
--- a/os/ports/GCC/ARMCMx/chcore_v6m.c
+++ b/os/ports/GCC/ARMCMx/chcore_v6m.c
@@ -32,11 +32,6 @@
  */
 regarm_t _port_saved_pc;
 
-/**
- * @brief   IRQ nesting counter.
- */
-unsigned _port_irq_nesting;
-
 /**
  * @brief   System Timer vector.
  * @details This interrupt is used as system tick.
diff --git a/os/ports/GCC/ARMCMx/chcore_v6m.h b/os/ports/GCC/ARMCMx/chcore_v6m.h
index 1bd2f777e..4b4ef04f6 100644
--- a/os/ports/GCC/ARMCMx/chcore_v6m.h
+++ b/os/ports/GCC/ARMCMx/chcore_v6m.h
@@ -118,11 +118,9 @@ struct intctx {
  * @details This macro must be inserted at the start of all IRQ handlers
  *          enabled to invoke system APIs.
  */
-#define PORT_IRQ_PROLOGUE() {                                               \
-  port_lock_from_isr();                                                     \
-  _port_irq_nesting++;                                                      \
-  port_unlock_from_isr();                                                   \
-}
+#define PORT_IRQ_PROLOGUE()                                                 \
+  regarm_t _saved_lr;                                                       \
+  asm volatile ("mov     %0, lr" : "=r" (_saved_lr) : : "memory")
 
 /**
  * @brief   IRQ epilogue code.
@@ -131,7 +129,7 @@ struct intctx {
  */
 #define PORT_IRQ_EPILOGUE() {                                               \
   port_lock_from_isr();                                                     \
-  if ((--_port_irq_nesting == 0) && chSchIsRescRequiredExI()) {             \
+  if ((_saved_lr != (regarm_t)0xFFFFFFF1) && chSchIsRescRequiredExI()) {    \
     register struct cmxctx *ctxp;                                           \
                                                                             \
     asm volatile ("mrs     %0, PSP" : "=r" (ctxp) : );                      \
@@ -160,7 +158,6 @@ struct intctx {
  * @brief   Port-related initialization code.
  */
 #define port_init() {                                                       \
-  _port_irq_nesting = 0;                                                    \
   SCB_AIRCR = AIRCR_VECTKEY | AIRCR_PRIGROUP(0);                            \
   NVICSetSystemHandlerPriority(HANDLER_SYSTICK,                             \
     CORTEX_PRIORITY_MASK(CORTEX_PRIORITY_SYSTICK));                         \
@@ -229,7 +226,6 @@ struct intctx {
 
 #if !defined(__DOXYGEN__)
 extern regarm_t _port_saved_pc;
-extern unsigned _port_irq_nesting;
 #endif
 
 #ifdef __cplusplus
diff --git a/readme.txt b/readme.txt
index 8516b1c41..6c5174cfa 100644
--- a/readme.txt
+++ b/readme.txt
@@ -69,6 +69,7 @@
 *****************************************************************************
 
 *** 2.3.0 ***
+- FIX: Fixed race condition in CM0 ports (bug 3193062)(backported to 2.2.2).
 - FIX: Fixed Cortex-Mx linker scripts alignment of __heap_base__, the
   correct alignment is now enforced at runtime into core_init() in order
   to make the OS integration easier (bug 3191112)(backported to 2.2.2).