From a8092c021d27f27f4b323b7d49979ca01b3fc19d Mon Sep 17 00:00:00 2001 From: Haavard Skinnemoen Date: Mon, 26 May 2008 12:19:10 +0200 Subject: [PATCH] avr32: Fix theoretical race in udelay() If the specified delay is very short, the cycle counter may go past the "end" time we are waiting for before we get around to reading it. Fix it by checking the different between the cycle count "now" and the cycle count at the beginning. This will work as long as the delay measured in number of cycles is below 2^31. Signed-off-by: Haavard Skinnemoen --- cpu/at32ap/interrupts.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/cpu/at32ap/interrupts.c b/cpu/at32ap/interrupts.c index bef1f30d79..160838eeeb 100644 --- a/cpu/at32ap/interrupts.c +++ b/cpu/at32ap/interrupts.c @@ -98,18 +98,16 @@ void set_timer(unsigned long t) */ void udelay(unsigned long usec) { - unsigned long now, end; + unsigned long cycles; + unsigned long base; + unsigned long now; - now = sysreg_read(COUNT); + base = sysreg_read(COUNT); + cycles = ((usec * (get_tbclk() / 10000)) + 50) / 100; - end = ((usec * (get_tbclk() / 10000)) + 50) / 100; - end += now; - - while (now > end) - now = sysreg_read(COUNT); - - while (now < end) + do { now = sysreg_read(COUNT); + } while ((now - base) < cycles); } static int set_interrupt_handler(unsigned int nr, void (*handler)(void), -- 2.30.2