Hi,
I womder what this patch (from 2.3.99.pre7.8 => 7.9) is supposed to
accomplish. perhaps somebody can enlighten me..?
drivers/char/tty_io.c: ... if(...!current->tty...) {
+ task_lock(current);
current->tty = tty;
+ task_unlock(current);
current->tty_old_pgrp = 0;
Since reads of current->tty are not locked, I fail to see any reason for
this change.
Same question, only worse, with this changed code (kernel/exit.c):
+ struct files_struct * files = tsk->files;
if (files) {
+ task_lock(tsk);
+ tsk->files = NULL;
+ task_unlock(tsk);
+ put_files_struct(files);
}
If two threads really can run this code at the same time, the locks
don't help. If not, they're unnecessary.
Better code:
task_lock(tsk);
if (tsk->files) {
struct files_struct * files = tsk->files;
tsk->files = NULL;
task_unlock(tsk);
put_files_struct(files);
} else
task_unlock(tsk);
or, since put_files_struct really doesn't take long and the additional
complexity is unnecessary, simply
task_lock(tsk);
if (tsk->files) {
put_files_struct(tsk->files);
tsk->files = NULL;
}
task_unlock(tsk);
Comments?
--
Matthias Urlichs | noris network GmbH | smurf@noris.de | ICQ: 20193661
The quote was selected randomly. Really. | http://smurf.noris.de/
--
The only solution is...a balance of power. We arm our side with exactly that
much more. A balance of power -- the trickiest, most difficult, dirtiest game
of them all. But the only one that preserves both sides.
-- Kirk, "A Private Little War," stardate 4211.8
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