[PATCH] set sigio target to current->pid and only if not already set
1. send_sigio() sends to a specific thread, _not_ a process.
(It can also send to a process group, but that's not relevant here).
This is useful, and should stay as it is.
Therefore it makes _no sense_ to call f_setown() with current->tgid.
Presently the kernel is inconsistent about it, with some places using
current->pid and some others using current->tgid.
This patch changes f_setown() calls to use current->pid.
2. In some places, f_setown() is called not at the user's direct request,
but as a side effect of another function. Specifically: dnotify and
file leases.
It is good to allow a program the flexibility to specify a different
pid than the default, using F_SETOWN. Presently they can do this after
the dnotify or lease call, but there is a small time window when it
will be temporarily set to current->tgid (which as pointed out above,
is not always right).
The window is avoidable if the program can use F_SETOWN prior to the
dnotify or lease call. This is exactly what the "force" argument to
f_setown() is for, and this patch changes it to zero in those callers.
This change is not likely to affect any existing programs.