Checking by the send function that at least two maximum size Ethernet frames fit in the remaining heap before the LwIP packet buffer is allocated seems to increase stability. This can be caused by the fact that WLAN hardware interrupts allocate additional memory when receiving a frame during the send attempt.
Error case:
1. thread_yield_higher() stores the thread's ucontext
2. creates an "isr ucontext" for isr_thread_yield, switches to it
Case 1: no signals are pending, continues in isr_thread_yield()
3a. sched_run is called
4a. return to sched_active_thread ucontext
Case 2: signals pending (the crashing scenario), continues in native_irq_handler()
3b. handles signals
4b. if sched_context_switch_request is set, call sched_run
5b. return to sched_active_thread ucontext
4b misses the call to sched_run(), leading to a possible return into a
non-ready thread.
The msp430 toolchain is missing an `fputs()` implementation. This commit makes
them use the `printf("%s", str);` instead of `fputs(str, stdout);`, which is
semantically equivalent (but has more overhead).
The LTC4150 is a coulomb counter (a.k.a. battery sensor or bidirectional
current sensor) that is used in the MSBA2 board and available for little money
as easy to use break out board.
Currently an interface's existence is not checked when it is supplied
by the user with the `nib` command. This can lead to assertion errors
as soon as the generated entry tries to resolve an address or route
generated with that command and the network interface not being found.
The situation where the firmware `lwIP` packet buffer is exhausted is an important indication that the traffic sent to and sent from the esp8266 is more than the esp8266 is able to handle. Therefore, it should be an error message.
It is not necessary to realize timeout handling in send function or to disconnect from AP if lwIP packet buffer is exhausted. Waiting that the frame allocated in lwIP packet buffer is freed by MAC layer led to the complete blockage of send function on heavy network load. Disconnecting from AP is counterproductive since reconnecting usually fails on heavy network load.
Disconnecting from the AP in the send function if the lwIP packet buffer is exhausted is counterproductive since reconnecting usually fails on heavy network load. A better strategy is to slow down the sending of MAC frames from netif a bit to wait for flushing the buffer in the MAC layer.
