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I found a problem with the last version. The attached is for
2.5.65-1.1171 (i.e. after the other post 2.5.65 changes). The bug is
fixed, and the code even simpler here.
The problem in the prior patch was that cascade should return:
(index +1) &... not index &...
Here I changed the call to cascade() to expect "index" back so it
checks for 0 instead of 1. Nice and simple.
-g
Tim Schmielau wrote:
> On Wed, 19 Mar 2003, george anzinger wrote:
>
>
>>In this case, the simple fix is to bump the
>>base->timer_jiffies at the beginning of the loop rather than the end.
>> This would cause the new timer to be put in the next jiffie instead
>>of the current one AND it is free!
>
>
> Yes, doing it this way looks correct to me.
>
>
>>>No, with the current implementation we need
>>> #define INDEX(N) (base->timer_jiffies >> (TVR_BITS + N * TVN_BITS) +1) &
>>> TVN_MASK
>>>although I'd like to see that cleaned up.
>>
>>I tried with the +1 and boot hangs trying to set up networking. I
>>think the difference is that the init code is trying to set things up
>>the way they would look AFTER cascade executes and this is doing it
>>BEFORE the cascade call.
>
>
> With the above change, it should be correct without the +1
>
>
>>>Why 'jiffies -1'? This will just be made up for in the first
>>>timer interrupt, where timer_jiffies will get incremented twice.
>>
>>Again, I removed the -1 in the attached.
>
>
> If you really want to be conservative, we'd better start with
> INITIAL_JIFFIES. Should be the same anyways. But if not, we might lose a
> timer scheduled for INITIAL_JIFFIES (not that I think it's possible to
> insert one before timer initialisation in the first place :-)
> or even a timer cascade.
>
>
>>>Did you bother to test the patch? It doesn't even boot for me, and I don't
>>>see how it is supposed to.
>>>I'll look into it more closely in the evening. Have to go to work now.
>>
>>The old one ran on 2.5.64 but not 2.5.65 ??? I found and fixed a bug
>>(index needs to be caculated INSIDE the while loop) that seems to have
>>been the cause.
>
>
> Ok will test in the evening.
>
> Tim
>
>
-- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml--=_courier-31008-1048109502-0001-2 Content-Type: text/plain; name="hrtimers-run-2.5.65-1.1171.patch"; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="hrtimers-run-2.5.65-1.1171.patch"
diff -urP -I '\$Id:.*Exp \$' -X /usr/src/patch.exclude linux-2.5.65-1.1171-kb/kernel/timer.c linux/kernel/timer.c --- linux-2.5.65-1.1171-kb/kernel/timer.c 2003-03-19 12:32:28.000000000 -0800 +++ linux/kernel/timer.c 2003-03-19 13:08:24.000000000 -0800 @@ -44,12 +44,10 @@ #define TVR_MASK (TVR_SIZE - 1) typedef struct tvec_s { - int index; struct list_head vec[TVN_SIZE]; } tvec_t; typedef struct tvec_root_s { - int index; struct list_head vec[TVR_SIZE]; } tvec_root_t; @@ -134,7 +132,7 @@ * Can happen if you add a timer with expires == jiffies, * or you set a timer to go off in the past */ - vec = base->tv1.vec + base->tv1.index; + vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK); } else if (idx <= 0xffffffffUL) { int i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK; vec = base->tv5.vec + i; @@ -368,12 +366,12 @@ #endif -static int cascade(tvec_base_t *base, tvec_t *tv) +static int cascade(tvec_base_t *base, tvec_t *tv, int index) { /* cascade all the timers from tv up one level */ struct list_head *head, *curr; - head = tv->vec + tv->index; + head = tv->vec + index; curr = head->next; /* * We are removing _all_ timers from the list, so we don't have to @@ -389,7 +387,7 @@ } INIT_LIST_HEAD(head); - return tv->index = (tv->index + 1) & TVN_MASK; + return index; } /*** @@ -399,6 +397,8 @@ * This function cascades all vectors and executes all expired timer * vectors. */ +#define INDEX(N) (base->timer_jiffies >> (TVR_BITS + N * TVN_BITS)) & TVN_MASK + static inline void __run_timers(tvec_base_t *base) { struct timer_list *timer; @@ -407,18 +407,19 @@ while (time_after_eq(jiffies, base->timer_jiffies)) { LIST_HEAD(deferred_timers); struct list_head *head; - + int index = base->timer_jiffies & TVR_MASK; + /* * Cascade timers: */ - if (!base->tv1.index && - (cascade(base, &base->tv2) == 1) && - (cascade(base, &base->tv3) == 1) && - cascade(base, &base->tv4) == 1) - cascade(base, &base->tv5); + if (!index && + (! cascade(base, &base->tv2, INDEX(0))) && + (! cascade(base, &base->tv3, INDEX(1))) && + ! cascade(base, &base->tv4, INDEX(2))) + cascade(base, &base->tv5, INDEX(3)); base->run_timer_list_running = &deferred_timers; repeat: - head = base->tv1.vec + base->tv1.index; + head = base->tv1.vec + index; if (!list_empty(head)) { void (*fn)(unsigned long); unsigned long data; @@ -437,7 +438,6 @@ } base->run_timer_list_running = NULL; ++base->timer_jiffies; - base->tv1.index = (base->tv1.index + 1) & TVR_MASK; while (!list_empty(&deferred_timers)) { timer = list_entry(deferred_timers.prev, struct timer_list, entry); @@ -1198,12 +1198,7 @@ for (j = 0; j < TVR_SIZE; j++) INIT_LIST_HEAD(base->tv1.vec + j); - base->timer_jiffies = INITIAL_JIFFIES; - base->tv1.index = INITIAL_JIFFIES & TVR_MASK; - base->tv2.index = (INITIAL_JIFFIES >> TVR_BITS) & TVN_MASK; - base->tv3.index = (INITIAL_JIFFIES >> (TVR_BITS+TVN_BITS)) & TVN_MASK; - base->tv4.index = (INITIAL_JIFFIES >> (TVR_BITS+2*TVN_BITS)) & TVN_MASK; - base->tv5.index = (INITIAL_JIFFIES >> (TVR_BITS+3*TVN_BITS)) & TVN_MASK; + base->timer_jiffies = jiffies; } static int __devinit timer_cpu_notify(struct notifier_block *self,
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