![Peter Zijlstra](/assets/img/avatar_default.png)
Commit d3d74453c3
("hrtimer: fixup the
HRTIMER_CB_IRQSAFE_NO_SOFTIRQ fallback") broke several archs, and since
only Russell bothered to merge the fix, and Greg to ACK his arch, I'm
sending this for merger.
I have confirmation that the Alpha bit results in a booting kernel.
That leaves: blackfin, frv, sh and sparc untested.
The deadlock in question was found by Russell:
IRQ handle
-> timer_tick() - xtime seqlock held for write
-> update_process_times()
-> run_local_timers()
-> hrtimer_run_queues()
-> hrtimer_get_softirq_time() - tries to get a read lock
Now, Thomas assures me the fix is trivial, only do_timer() needs to be
done under the xtime_lock, and update_process_times() can savely be
removed from under it.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Greg Ungerer <gerg@uclinux.org>
CC: Richard Henderson <rth@twiddle.net>
CC: Bryan Wu <bryan.wu@analog.com>
CC: David Howells <dhowells@redhat.com>
CC: Paul Mundt <lethal@linux-sh.org>
CC: William Irwin <wli@holomorphy.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
259 lines
6.7 KiB
C
259 lines
6.7 KiB
C
/*
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* File: arch/blackfin/kernel/time.c
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* Based on: none - original work
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* Author:
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*
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* Created:
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* Description: This file contains the bfin-specific time handling details.
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* Most of the stuff is located in the machine specific files.
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*
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* Modified:
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* Copyright 2004-2006 Analog Devices Inc.
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*
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* Bugs: Enter bugs at http://blackfin.uclinux.org/
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see the file COPYING, or write
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* to the Free Software Foundation, Inc.,
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* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <linux/module.h>
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#include <linux/profile.h>
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#include <linux/interrupt.h>
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#include <linux/time.h>
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#include <linux/irq.h>
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#include <asm/blackfin.h>
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/* This is an NTP setting */
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#define TICK_SIZE (tick_nsec / 1000)
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static void time_sched_init(irqreturn_t(*timer_routine)
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(int, void *));
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static unsigned long gettimeoffset(void);
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static struct irqaction bfin_timer_irq = {
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.name = "BFIN Timer Tick",
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.flags = IRQF_DISABLED
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};
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/*
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* The way that the Blackfin core timer works is:
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* - CCLK is divided by a programmable 8-bit pre-scaler (TSCALE)
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* - Every time TSCALE ticks, a 32bit is counted down (TCOUNT)
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*
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* If you take the fastest clock (1ns, or 1GHz to make the math work easier)
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* 10ms is 10,000,000 clock ticks, which fits easy into a 32-bit counter
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* (32 bit counter is 4,294,967,296ns or 4.2 seconds) so, we don't need
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* to use TSCALE, and program it to zero (which is pass CCLK through).
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* If you feel like using it, try to keep HZ * TIMESCALE to some
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* value that divides easy (like power of 2).
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*/
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#define TIME_SCALE 1
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static void
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time_sched_init(irqreturn_t(*timer_routine) (int, void *))
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{
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u32 tcount;
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/* power up the timer, but don't enable it just yet */
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bfin_write_TCNTL(1);
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CSYNC();
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/*
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* the TSCALE prescaler counter.
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*/
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bfin_write_TSCALE((TIME_SCALE - 1));
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tcount = ((get_cclk() / (HZ * TIME_SCALE)) - 1);
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bfin_write_TPERIOD(tcount);
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bfin_write_TCOUNT(tcount);
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/* now enable the timer */
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CSYNC();
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bfin_write_TCNTL(7);
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bfin_timer_irq.handler = (irq_handler_t)timer_routine;
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/* call setup_irq instead of request_irq because request_irq calls
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* kmalloc which has not been initialized yet
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*/
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setup_irq(IRQ_CORETMR, &bfin_timer_irq);
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}
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/*
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* Should return useconds since last timer tick
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*/
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static unsigned long gettimeoffset(void)
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{
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unsigned long offset;
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unsigned long clocks_per_jiffy;
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clocks_per_jiffy = bfin_read_TPERIOD();
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offset =
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(clocks_per_jiffy -
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bfin_read_TCOUNT()) / (((clocks_per_jiffy + 1) * HZ) /
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USEC_PER_SEC);
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/* Check if we just wrapped the counters and maybe missed a tick */
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if ((bfin_read_ILAT() & (1 << IRQ_CORETMR))
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&& (offset < (100000 / HZ / 2)))
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offset += (USEC_PER_SEC / HZ);
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return offset;
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}
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static inline int set_rtc_mmss(unsigned long nowtime)
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{
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return 0;
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}
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/*
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* timer_interrupt() needs to keep up the real-time clock,
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* as well as call the "do_timer()" routine every clocktick
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*/
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#ifdef CONFIG_CORE_TIMER_IRQ_L1
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irqreturn_t timer_interrupt(int irq, void *dummy)__attribute__((l1_text));
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#endif
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irqreturn_t timer_interrupt(int irq, void *dummy)
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{
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/* last time the cmos clock got updated */
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static long last_rtc_update;
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write_seqlock(&xtime_lock);
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do_timer(1);
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profile_tick(CPU_PROFILING);
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/*
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* If we have an externally synchronized Linux clock, then update
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* CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
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* called as close as possible to 500 ms before the new second starts.
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*/
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if (ntp_synced() &&
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xtime.tv_sec > last_rtc_update + 660 &&
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(xtime.tv_nsec / NSEC_PER_USEC) >=
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500000 - ((unsigned)TICK_SIZE) / 2
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&& (xtime.tv_nsec / NSEC_PER_USEC) <=
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500000 + ((unsigned)TICK_SIZE) / 2) {
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if (set_rtc_mmss(xtime.tv_sec) == 0)
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last_rtc_update = xtime.tv_sec;
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else
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/* Do it again in 60s. */
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last_rtc_update = xtime.tv_sec - 600;
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}
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write_sequnlock(&xtime_lock);
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#ifndef CONFIG_SMP
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update_process_times(user_mode(get_irq_regs()));
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#endif
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return IRQ_HANDLED;
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}
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void __init time_init(void)
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{
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time_t secs_since_1970 = (365 * 37 + 9) * 24 * 60 * 60; /* 1 Jan 2007 */
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#ifdef CONFIG_RTC_DRV_BFIN
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/* [#2663] hack to filter junk RTC values that would cause
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* userspace to have to deal with time values greater than
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* 2^31 seconds (which uClibc cannot cope with yet)
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*/
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if ((bfin_read_RTC_STAT() & 0xC0000000) == 0xC0000000) {
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printk(KERN_NOTICE "bfin-rtc: invalid date; resetting\n");
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bfin_write_RTC_STAT(0);
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}
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#endif
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/* Initialize xtime. From now on, xtime is updated with timer interrupts */
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xtime.tv_sec = secs_since_1970;
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xtime.tv_nsec = 0;
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wall_to_monotonic.tv_sec = -xtime.tv_sec;
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time_sched_init(timer_interrupt);
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}
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#ifndef CONFIG_GENERIC_TIME
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void do_gettimeofday(struct timeval *tv)
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{
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unsigned long flags;
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unsigned long seq;
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unsigned long usec, sec;
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do {
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seq = read_seqbegin_irqsave(&xtime_lock, flags);
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usec = gettimeoffset();
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sec = xtime.tv_sec;
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usec += (xtime.tv_nsec / NSEC_PER_USEC);
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}
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while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
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while (usec >= USEC_PER_SEC) {
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usec -= USEC_PER_SEC;
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sec++;
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}
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tv->tv_sec = sec;
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tv->tv_usec = usec;
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}
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EXPORT_SYMBOL(do_gettimeofday);
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int do_settimeofday(struct timespec *tv)
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{
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time_t wtm_sec, sec = tv->tv_sec;
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long wtm_nsec, nsec = tv->tv_nsec;
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if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
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return -EINVAL;
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write_seqlock_irq(&xtime_lock);
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/*
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* This is revolting. We need to set the xtime.tv_usec
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* correctly. However, the value in this location is
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* is value at the last tick.
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* Discover what correction gettimeofday
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* would have done, and then undo it!
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*/
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nsec -= (gettimeoffset() * NSEC_PER_USEC);
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wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
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wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
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set_normalized_timespec(&xtime, sec, nsec);
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set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
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ntp_clear();
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write_sequnlock_irq(&xtime_lock);
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clock_was_set();
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return 0;
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}
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EXPORT_SYMBOL(do_settimeofday);
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#endif /* !CONFIG_GENERIC_TIME */
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/*
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* Scheduler clock - returns current time in nanosec units.
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*/
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unsigned long long sched_clock(void)
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{
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return (unsigned long long)jiffies *(NSEC_PER_SEC / HZ);
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}
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