Hi! This is a driver-related question on non-blocking writes and poll.
Setup: there is a single output-buffer (in kernel-space) of 24 bytes for writes from all processes A, B, and C: each process is restricted to use at most 8 bytes: 8*3 = 24 (until that data is handled (interrupt-handler...)) Question: If this output-buffer has "4-bytes space remaining for process A", then a non-blocking write of process A could still encounter a locked mutex, if process B is busy writing to the output-buffer. Should process A now block/sleep until that mutex is free and it can access the output-buffer (and it's 4 bytes space)? What about a non-blocking (write-) poll of process A: if the poll call succeeds (the output buffer has space remaining for process A), and process A now performs a non-blocking write: what happens if A encounters a blocked mutex, since process B is busy writing to the output-buffer. a) Should A block until the mutex is available? b) Should A return -EAGAIN, even though the poll call succeeded? c) Should it be impossible for this to happen! i.e. -> should process A already "have" the mutex in question, when the poll call succeeds (thus preventing B from writing to the output buffer) For c) What if process A "has" the mutex, but never does the non-blocking write. Then no process can write, since the mutex is held by process A... I'll appreciate any answer, or pointer to relevant information. Thanks Albert - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
