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openvswitch/datapath/loop_counter.c

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datapath: Add loop detection for RT kernels. Our normal loop detection requires disabling preemption while packet processing takes place. On RT kernels this isn't acceptable and interacts badly with spinlocks, so we can't use it. This takes advantage of some extra space that is added to struct task_struct on RT kernels (and the knowledge that we will always have a valid task_struct) to store the loop counter for a given thread. Since we can't make these assumptions on non-RT kernels, we continue to use the previous method of loop detection there. Signed-off-by: Jesse Gross <jesse@nicira.com> Acked-by: Ben Pfaff <blp@nicira.com>
2010-10-18 15:30:20 -07:00
/*
* Distributed under the terms of the GNU GPL version 2.
datapath: Drop parameters from execute_actions(). It's (almost) always easier to understand a function with fewer parameters, so this removes the now-redundant sw_flow_key and actions parameters from execute_actions(), since they can be found through OVS_CB(skb)->flow now. This also necessarily moves loop detection into execute_actions(). Otherwise, the flow's actions could have changed between the time that the loop was detected and the time that it was suppressed, which would mean that the wrong (version of the) flow would get suppressed. Signed-off-by: Ben Pfaff <blp@nicira.com> Acked-by: Jesse Gross <jesse@nicira.com>
2011-04-29 10:49:06 -07:00
* Copyright (c) 2010, 2011 Nicira Networks.
datapath: Add loop detection for RT kernels. Our normal loop detection requires disabling preemption while packet processing takes place. On RT kernels this isn't acceptable and interacts badly with spinlocks, so we can't use it. This takes advantage of some extra space that is added to struct task_struct on RT kernels (and the knowledge that we will always have a valid task_struct) to store the loop counter for a given thread. Since we can't make these assumptions on non-RT kernels, we continue to use the previous method of loop detection there. Signed-off-by: Jesse Gross <jesse@nicira.com> Acked-by: Ben Pfaff <blp@nicira.com>
2010-10-18 15:30:20 -07:00
*
* Significant portions of this file may be copied from parts of the Linux
* kernel, by Linus Torvalds and others.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/hardirq.h>
#include <linux/kernel.h>
#include <linux/percpu.h>
#include <linux/sched.h>
#include "loop_counter.h"
datapath: Drop parameters from execute_actions(). It's (almost) always easier to understand a function with fewer parameters, so this removes the now-redundant sw_flow_key and actions parameters from execute_actions(), since they can be found through OVS_CB(skb)->flow now. This also necessarily moves loop detection into execute_actions(). Otherwise, the flow's actions could have changed between the time that the loop was detected and the time that it was suppressed, which would mean that the wrong (version of the) flow would get suppressed. Signed-off-by: Ben Pfaff <blp@nicira.com> Acked-by: Jesse Gross <jesse@nicira.com>
2011-04-29 10:49:06 -07:00
int loop_suppress(struct datapath *dp, struct sw_flow_actions *actions)
datapath: Add loop detection for RT kernels. Our normal loop detection requires disabling preemption while packet processing takes place. On RT kernels this isn't acceptable and interacts badly with spinlocks, so we can't use it. This takes advantage of some extra space that is added to struct task_struct on RT kernels (and the knowledge that we will always have a valid task_struct) to store the loop counter for a given thread. Since we can't make these assumptions on non-RT kernels, we continue to use the previous method of loop detection there. Signed-off-by: Jesse Gross <jesse@nicira.com> Acked-by: Ben Pfaff <blp@nicira.com>
2010-10-18 15:30:20 -07:00
{
if (net_ratelimit())
pr_warn("%s: flow looped %d times, dropping\n",
dp_name(dp), MAX_LOOPS);
datapath: Replace "struct odp_action" by Netlink attributes. In the medium term, we plan to migrate the datapath to use Netlink as its communication channel. In the short term, we need to be able to have actions with 64-bit arguments but "struct odp_action" only has room for 48 bits. So this patch shifts to variable-length arguments using Netlink attributes, which starts in on the Netlink transition and makes 64-bit arguments possible at the same time. Signed-off-by: Ben Pfaff <blp@nicira.com> Acked-by: Jesse Gross <jesse@nicira.com>
2010-12-10 10:40:58 -08:00
actions->actions_len = 0;
datapath: Drop parameters from execute_actions(). It's (almost) always easier to understand a function with fewer parameters, so this removes the now-redundant sw_flow_key and actions parameters from execute_actions(), since they can be found through OVS_CB(skb)->flow now. This also necessarily moves loop detection into execute_actions(). Otherwise, the flow's actions could have changed between the time that the loop was detected and the time that it was suppressed, which would mean that the wrong (version of the) flow would get suppressed. Signed-off-by: Ben Pfaff <blp@nicira.com> Acked-by: Jesse Gross <jesse@nicira.com>
2011-04-29 10:49:06 -07:00
return -ELOOP;
datapath: Add loop detection for RT kernels. Our normal loop detection requires disabling preemption while packet processing takes place. On RT kernels this isn't acceptable and interacts badly with spinlocks, so we can't use it. This takes advantage of some extra space that is added to struct task_struct on RT kernels (and the knowledge that we will always have a valid task_struct) to store the loop counter for a given thread. Since we can't make these assumptions on non-RT kernels, we continue to use the previous method of loop detection there. Signed-off-by: Jesse Gross <jesse@nicira.com> Acked-by: Ben Pfaff <blp@nicira.com>
2010-10-18 15:30:20 -07:00
}
#ifndef CONFIG_PREEMPT_RT
/* We use a separate counter for each CPU for both interrupt and non-interrupt
* context in order to keep the limit deterministic for a given packet.
*/
struct percpu_loop_counters {
struct loop_counter counters[2];
};
static DEFINE_PER_CPU(struct percpu_loop_counters, loop_counters);
struct loop_counter *loop_get_counter(void)
{
return &get_cpu_var(loop_counters).counters[!!in_interrupt()];
}
void loop_put_counter(void)
{
put_cpu_var(loop_counters);
}
#else /* !CONFIG_PREEMPT_RT */
struct loop_counter *loop_get_counter(void)
{
WARN_ON(in_interrupt());
/* Only two bits of the extra_flags field in struct task_struct are
* used and it's an unsigned int. We hijack the most significant bits
* to be our counter structure. On RT kernels softirqs always run in
* process context so we are guaranteed to have a valid task_struct.
*/
#ifdef __LITTLE_ENDIAN
return (void *)(&current->extra_flags + 1) -
sizeof(struct loop_counter);
#elif __BIG_ENDIAN
return (struct loop_counter *)&current->extra_flags;
#else
#error "Please fix <asm/byteorder.h>."
#endif
}
void loop_put_counter(void) { }
#endif /* CONFIG_PREEMPT_RT */
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