x86/hpet: Use the FSEC_PER_SEC constant for femto-second periods (4936a3b9) · Commits · 戴 / test

The current computation, introduced with , of FSEC_PER_SEC using the multiplication of (FSEC_PER_NSEC * NSEC_PER_SEC) is performed only with 32bit integers on small machines, resulting in an overflow and a *very* short intervals being programmed. An interrupt storm follows. Note that we also have to specify FSEC_PER_SEC as being long long to overcome the same limitations. Signed-off-by:

Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by:

John Stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Acked-by:

Ingo Molnar <mingo@elte.hu> Acked-by:

H. Peter Anvin <hpa@zytor.com> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/kernel/hpet.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -582,7 +582,7 @@ static void init_one_hpet_msi_clockevent(struct hpet_dev *hdev, int cpu)
		* scaled math multiplication factor for nanosecond to hpet tick
		* conversion.
		*/
		hpet_freq = 1000000000000000ULL;
		hpet_freq = FSEC_PER_SEC;
		do_div(hpet_freq, hpet_period);
		evt->mult = div_sc((unsigned long) hpet_freq,
		NSEC_PER_SEC, evt->shift);
		@@ -837,7 +837,7 @@ static int hpet_clocksource_register(void)
		* cyc/sec = FSEC_PER_SEC/hpet_period(fsec/cyc)
		* cyc/sec = (FSEC_PER_NSEC * NSEC_PER_SEC)/hpet_period
		*/
		hpet_freq = FSEC_PER_NSEC * NSEC_PER_SEC;
		hpet_freq = FSEC_PER_SEC;
		do_div(hpet_freq, hpet_period);
		clocksource_register_hz(&clocksource_hpet, (u32)hpet_freq);

include/linux/time.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -38,7 +38,7 @@ extern struct timezone sys_tz;
		#define NSEC_PER_MSEC 1000000L
		#define USEC_PER_SEC 1000000L
		#define NSEC_PER_SEC 1000000000L
		#define FSEC_PER_SEC 1000000000000000L
		#define FSEC_PER_SEC 1000000000000000LL

		#define TIME_T_MAX (time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1)

Admin message