Re: [lwip-users] Lock in tcp_in

[Simon Goldschmidt]

You should specificaly pay attention to the timers: they are executed within 
the semaphore/mbox functions (sys_sem_*/sys_mbox_*) and fetch a list of 
timeouts from an arch-dependent function. This list must be per-thread - if 
not, timers will be executed in a wrong thread, which may lead to the 
pcb-list-corruption you saw (by executing tcp_tmr() outside tcpip_thread 
context).

Simon


Lou Cypher wrote:
> > Such bugs with corrupt PCB lists have always in the past been two
> > threads (e.g. interrupt, timer, or application) active in lwIP at the
> > same time.  This fits very well with your description.
> 
> I know it has all the characteristics of data corruption by interrupt
> handling
> and/or task switching, and I'll look further in that direction.
> Even though I should have no reason for unexpected reentrancy/data access,
> with
> cooperative multitasking.
> All the system's interrupts are unrelated to lwIP, besides the MAC
> controller of
> course: but it puts data in a queue unknown to lwIP, and it's later
> extracted
> (atomically) by a task dedicated to lwIP processing.
> 
> ~ Lou
> 
> 
> 
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