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[You-Sheng Yang <1408239@xxxxxxxxxxxxxxxxxx>]

** Changed in: ofono (Ubuntu)
       Status: In Progress => Won't Fix

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https://bugs.launchpad.net/bugs/1408239

Title:
  refactor GRil incoming bytes dispatching mechanism

Status in ofono package in Ubuntu:
  Won't Fix

Bug description:
  GRil reads incoming bytes into ril_msg structure in function
  `read_fixed_record` in gril/gril.c. It's mostly working except it
  makes some assumptions that are not always true.

  1. The `read_fixed_record` function calls `memmove` to copy data from
  ring_buffer, which follows that the whole parcel must not be wrapped.
  This is usually true because whenever a parcel is read, the
  ring_buffer rewind its in/out position markers to the beginning.
  However, if somehow rild transmits massive amount of parcels, or due
  to various reasons that the gio thread is not waked up in time and a
  lot of incoming data queued in kernel, then a parcel that spans across
  the boundary becomes very likely. This is actually the question raised
  in the comment:

    /* TODO: need to better understand how wrap works! */

  With https://bugs.launchpad.net/ubuntu/+source/ofono/+bug/1408228, the
  GrilIO part is immune from this problem but the `read_fixed_record` is
  still affected.

  2. One should really avoid using ring_buffer APIs that involve its
  internal states. Ring buffer wrapping should not be a concern to other
  components whenever possible.

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