[lwip-devel] [bug #27791] null pointer dereference (pcb->unacked == 0) in tcp_in.c:tcp_process

[Guillaume du PONTAVICE]

Follow-up Comment #4, bug #27791 (project lwip):

please find more details on my environment :

platform ST7109 chipset (SH4 core)
I use OS21 operating system (ST operating system, supporting thread,
semaphore, mailbox, ...)
ethernet chipset : STMAC (supporting 100 Mb/s FD, DMA ...)

my application uses sockets.

ethernet driver : 
reception is done thanks to ISR. 
ISR wakes up a dedicated task that calls ip_input()

transmission is synchronous. when exiting netif->output function, the packet
is really sent on the network.

in my current config, the asynchronous reception task can be woken up in the
middle of a packet transmission.

however, even if I add a lock that forbids a packet reception while a packet
is transmitted, it won't solve the problem :

in my scenario, the packet reception does not happen when i am in
tcp_output_segment. it happens just after.

maybe a workaround could be to put a higher priority on tcpip_thread task, to
ensure that the asynchronous reception task won't disturb it ?

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