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48d83325b6
linux/include/net/pkt_sched.h
Herbert Xu 48d83325b6 [NET]: Prevent multiple qdisc runs 
Having two or more qdisc_run's contend against each other is bad because
it can induce packet reordering if the packets have to be requeued.  It
appears that this is an unintended consequence of relinquinshing the queue
lock while transmitting.  That in turn is needed for devices that spend a
lot of time in their transmit routine.

There are no advantages to be had as devices with queues are inherently
single-threaded (the loopback device is not but then it doesn't have a
queue).

Even if you were to add a queue to a parallel virtual device (e.g., bolt
a tbf filter in front of an ipip tunnel device), you would still want to
process the queue in sequence to ensure that the packets are ordered
correctly.

The solution here is to steal a bit from net_device to prevent this.

BTW, as qdisc_restart is no longer used by anyone as a module inside the
kernel (IIRC it used to with netif_wake_queue), I have not exported the
new __qdisc_run function.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-06-19 23:57:59 -07:00

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#ifndef __NET_PKT_SCHED_H
#define __NET_PKT_SCHED_H
#include <linux/jiffies.h>
#include <net/sch_generic.h>
struct qdisc_walker
{
int stop;
int skip;
int count;
int (*fn)(struct Qdisc *, unsigned long cl, struct qdisc_walker *);
};
extern rwlock_t qdisc_tree_lock;
#define QDISC_ALIGNTO 32
#define QDISC_ALIGN(len) (((len) + QDISC_ALIGNTO-1) & ~(QDISC_ALIGNTO-1))
static inline void *qdisc_priv(struct Qdisc *q)
{
return (char *) q + QDISC_ALIGN(sizeof(struct Qdisc));
}
/*
Timer resolution MUST BE < 10% of min_schedulable_packet_size/bandwidth
Normal IP packet size ~ 512byte, hence:
0.5Kbyte/1Mbyte/sec = 0.5msec, so that we need 50usec timer for
10Mbit ethernet.
10msec resolution -> <50Kbit/sec.
The result: [34]86 is not good choice for QoS router :-(
The things are not so bad, because we may use artifical
clock evaluated by integration of network data flow
in the most critical places.
Note: we do not use fastgettimeofday.
The reason is that, when it is not the same thing as
gettimeofday, it returns invalid timestamp, which is
not updated, when net_bh is active.
*/
/* General note about internal clock.
Any clock source returns time intervals, measured in units
close to 1usec. With source CONFIG_NET_SCH_CLK_GETTIMEOFDAY it is precisely
microseconds, otherwise something close but different chosen to minimize
arithmetic cost. Ratio usec/internal untis in form nominator/denominator
may be read from /proc/net/psched.
*/
#ifdef CONFIG_NET_SCH_CLK_GETTIMEOFDAY
typedef struct timeval psched_time_t;
typedef long psched_tdiff_t;
#define PSCHED_GET_TIME(stamp) do_gettimeofday(&(stamp))
#define PSCHED_US2JIFFIE(usecs) usecs_to_jiffies(usecs)
#define PSCHED_JIFFIE2US(delay) jiffies_to_usecs(delay)
#else /* !CONFIG_NET_SCH_CLK_GETTIMEOFDAY */
typedef u64 psched_time_t;
typedef long psched_tdiff_t;
#ifdef CONFIG_NET_SCH_CLK_JIFFIES
#if HZ < 96
#define PSCHED_JSCALE 14
#elif HZ >= 96 && HZ < 192
#define PSCHED_JSCALE 13
#elif HZ >= 192 && HZ < 384
#define PSCHED_JSCALE 12
#elif HZ >= 384 && HZ < 768
#define PSCHED_JSCALE 11
#elif HZ >= 768
#define PSCHED_JSCALE 10
#endif
#define PSCHED_GET_TIME(stamp) ((stamp) = (get_jiffies_64()<<PSCHED_JSCALE))
#define PSCHED_US2JIFFIE(delay) (((delay)+(1<<PSCHED_JSCALE)-1)>>PSCHED_JSCALE)
#define PSCHED_JIFFIE2US(delay) ((delay)<<PSCHED_JSCALE)
#endif /* CONFIG_NET_SCH_CLK_JIFFIES */
#ifdef CONFIG_NET_SCH_CLK_CPU
#include <asm/timex.h>
extern psched_tdiff_t psched_clock_per_hz;
extern int psched_clock_scale;
extern psched_time_t psched_time_base;
extern cycles_t psched_time_mark;
#define PSCHED_GET_TIME(stamp) \
do { \
cycles_t cur = get_cycles(); \
if (sizeof(cycles_t) == sizeof(u32)) { \
if (cur <= psched_time_mark) \
psched_time_base += 0x100000000ULL; \
psched_time_mark = cur; \
(stamp) = (psched_time_base + cur)>>psched_clock_scale; \
} else { \
(stamp) = cur>>psched_clock_scale; \
} \
} while (0)
#define PSCHED_US2JIFFIE(delay) (((delay)+psched_clock_per_hz-1)/psched_clock_per_hz)
#define PSCHED_JIFFIE2US(delay) ((delay)*psched_clock_per_hz)
#endif /* CONFIG_NET_SCH_CLK_CPU */
#endif /* !CONFIG_NET_SCH_CLK_GETTIMEOFDAY */
#ifdef CONFIG_NET_SCH_CLK_GETTIMEOFDAY
#define PSCHED_TDIFF(tv1, tv2) \
({ \
int __delta_sec = (tv1).tv_sec - (tv2).tv_sec; \
int __delta = (tv1).tv_usec - (tv2).tv_usec; \
if (__delta_sec) { \
switch (__delta_sec) { \
default: \
__delta = 0; \
case 2: \
__delta += USEC_PER_SEC; \
case 1: \
__delta += USEC_PER_SEC; \
} \
} \
__delta; \
})
static inline int
psched_tod_diff(int delta_sec, int bound)
{
int delta;
if (bound <= USEC_PER_SEC || delta_sec > (0x7FFFFFFF/USEC_PER_SEC)-1)
return bound;
delta = delta_sec * USEC_PER_SEC;
if (delta > bound || delta < 0)
delta = bound;
return delta;
}
#define PSCHED_TDIFF_SAFE(tv1, tv2, bound) \
({ \
int __delta_sec = (tv1).tv_sec - (tv2).tv_sec; \
int __delta = (tv1).tv_usec - (tv2).tv_usec; \
switch (__delta_sec) { \
default: \
__delta = psched_tod_diff(__delta_sec, bound); break; \
case 2: \
__delta += USEC_PER_SEC; \
case 1: \
__delta += USEC_PER_SEC; \
case 0: \
if (__delta > bound || __delta < 0) \
__delta = bound; \
} \
__delta; \
})
#define PSCHED_TLESS(tv1, tv2) (((tv1).tv_usec < (tv2).tv_usec && \
(tv1).tv_sec <= (tv2).tv_sec) || \
(tv1).tv_sec < (tv2).tv_sec)
#define PSCHED_TADD2(tv, delta, tv_res) \
({ \
int __delta = (tv).tv_usec + (delta); \
(tv_res).tv_sec = (tv).tv_sec; \
if (__delta > USEC_PER_SEC) { (tv_res).tv_sec++; __delta -= USEC_PER_SEC; } \
(tv_res).tv_usec = __delta; \
})
#define PSCHED_TADD(tv, delta) \
({ \
(tv).tv_usec += (delta); \
if ((tv).tv_usec > USEC_PER_SEC) { (tv).tv_sec++; \
(tv).tv_usec -= USEC_PER_SEC; } \
})
/* Set/check that time is in the "past perfect";
it depends on concrete representation of system time
*/
#define PSCHED_SET_PASTPERFECT(t) ((t).tv_sec = 0)
#define PSCHED_IS_PASTPERFECT(t) ((t).tv_sec == 0)
#define PSCHED_AUDIT_TDIFF(t) ({ if ((t) > 2000000) (t) = 2000000; })
#else /* !CONFIG_NET_SCH_CLK_GETTIMEOFDAY */
#define PSCHED_TDIFF(tv1, tv2) (long)((tv1) - (tv2))
#define PSCHED_TDIFF_SAFE(tv1, tv2, bound) \
min_t(long long, (tv1) - (tv2), bound)
#define PSCHED_TLESS(tv1, tv2) ((tv1) < (tv2))
#define PSCHED_TADD2(tv, delta, tv_res) ((tv_res) = (tv) + (delta))
#define PSCHED_TADD(tv, delta) ((tv) += (delta))
#define PSCHED_SET_PASTPERFECT(t) ((t) = 0)
#define PSCHED_IS_PASTPERFECT(t) ((t) == 0)
#define PSCHED_AUDIT_TDIFF(t)
#endif /* !CONFIG_NET_SCH_CLK_GETTIMEOFDAY */
extern struct Qdisc_ops pfifo_qdisc_ops;
extern struct Qdisc_ops bfifo_qdisc_ops;
extern int register_qdisc(struct Qdisc_ops *qops);
extern int unregister_qdisc(struct Qdisc_ops *qops);
extern struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle);
extern struct Qdisc *qdisc_lookup_class(struct net_device *dev, u32 handle);
extern struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,
struct rtattr *tab);
extern void qdisc_put_rtab(struct qdisc_rate_table *tab);
extern void __qdisc_run(struct net_device *dev);
static inline void qdisc_run(struct net_device *dev)
{
if (!netif_queue_stopped(dev) &&
!test_and_set_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
__qdisc_run(dev);
}
extern int tc_classify(struct sk_buff *skb, struct tcf_proto *tp,
struct tcf_result *res);
/* Calculate maximal size of packet seen by hard_start_xmit
routine of this device.
*/
static inline unsigned psched_mtu(struct net_device *dev)
{
unsigned mtu = dev->mtu;
return dev->hard_header ? mtu + dev->hard_header_len : mtu;
}
#endif
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