STM32: flash: make flash_wait() a voluntary preemption point

A process that writes large chunks of data to the embedded flash can
monopolize the CPU for a very long time if the flash is fast enough to
write data words.

This is bad from the real-time perspective, so make flash_wait() a
voluntary preemption point, also in the case when the flash is fast
enough and never goes in busy state.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@4771 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/bertos/cpu/cortex-m3/drv/flash_stm32.c b/bertos/cpu/cortex-m3/drv/flash_stm32.c
index 816cdd58f94096f459a240f6a18f386cdc665328..d92e91420cbb67bd5ce3171e76679c03d11ac305 100644 (file)
--- a/bertos/cpu/cortex-m3/drv/flash_stm32.c
+++ b/bertos/cpu/cortex-m3/drv/flash_stm32.c
@@ -67,6 +67,7 @@ static bool flash_wait(struct KBlock *blk)
        ticks_t start = timer_clock();
        while (true)
        {
+               cpu_relax();
                if (!(EMB_FLASH->SR & FLASH_FLAG_BSY))
                        break;
 
@@ -90,8 +91,6 @@ static bool flash_wait(struct KBlock *blk)
                        LOG_ERR("Timeout..\n");
                        return false;
                }
-
-               cpu_relax();
        }
 
        return true;