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Enforce COOP priorities for networking subsystem #8386

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Enforce COOP priorities for networking subsystem #8386

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f72c3de
kconfig: Set main thread priority to -1 if cooperative
jukkar Jun 14, 2018
a57572a
net: Require that system workqueue priority < 0
jukkar Jun 14, 2018
8dcae2c
net: Make sure CONFIG_COOP_ENABLED is set
jukkar Jun 14, 2018
072afc1
net: Add build check for main thread priority
jukkar Jun 14, 2018
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1 change: 1 addition & 0 deletions kernel/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,7 @@ config MAIN_THREAD_PRIORITY
int
prompt "Priority of initialization/main thread"
default 0
default -1 if COOP_ENABLED
default -2 if !PREEMPT_ENABLED
help
Priority at which the initialization thread runs, including the start
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6 changes: 6 additions & 0 deletions subsys/net/Kconfig
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Expand Up @@ -85,12 +85,18 @@ config NETWORKING
select NET_BUF
select POLL
select ENTROPY_GENERATOR
select COOP_ENABLED
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@SebastianBoe SebastianBoe Jun 14, 2018

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I don't think this actually does anything useful.

You can test this by trying to come up with a situation where this select prevents an invalid configuration from occuring.

default n
help
This option enabled generic link layer and IP networking support.

if NETWORKING

# The networking subsystem requires the system workqueue to execute at
# a cooperative priority.
config SYSTEM_WORKQUEUE_PRIORITY
range -256 -1

source "subsys/net/Kconfig.hostname"

source "subsys/net/ip/Kconfig"
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7 changes: 7 additions & 0 deletions subsys/net/ip/net_core.c
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Expand Up @@ -419,4 +419,11 @@ static int net_init(struct device *unused)
return status;
}

/* The networking subsystem requires the main thread to execute at a
* cooperative priority to function correctly. If this build assert triggers
* verify your configuration to ensure that cooperative threads are enabled
* and that the main thread priority is negative (cooperative).
*/
BUILD_ASSERT(CONFIG_MAIN_THREAD_PRIORITY < 0);

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@SebastianBoe SebastianBoe Jun 14, 2018

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Invalid configurations should be detected during configuration instead
of during compilation whenever possible.

I believe that adding the below at an appropriate net Kconfig location would achieve this.

# The networking subsystem requires the main thread to execute at
# a cooperative priority.
config MAIN_THREAD_PRIORITY
	range -256 -1

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@andyross andyross Jun 14, 2018

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I don't see that this is going to do much anyway. The fact that the main thread is or is not preemptible says nothing about users of the network APIs which may or may not be running in the main thread. Not, for example, that ztest always spawns a new thread for every test, so none of the existing tests would be caught by this check if they happened to be hitting the network out of a preemptible thread.

I'd suggest a runtime __ASSERT(k_thread_prioroity_get(k_current_get() < 0) at the relevant API entry points.

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@jukkar jukkar Jun 15, 2018

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I believe that adding the below at an appropriate net Kconfig location would achieve this.
config MAIN_THREAD_PRIORITY
range -256 -1

This will give error if the default MAIN_THREAD_PRIORITY is 0. In which case user needs to add the proper value into prj.conf file. This PR tries to avoid this.

SYS_INIT(net_init, POST_KERNEL, CONFIG_NET_INIT_PRIO);