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/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
