linux-kernel - Deleting timers

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Message-ID: <Pine.LNX.4.44L0.0906261535140.4155-100000@iolanthe.rowland.org>
Date:	Fri, 26 Jun 2009 15:50:54 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Deleting timers

Thomas:

The major difference -- in fact, almost the only difference -- between
del_timer() and try_to_del_timer_sync() is that try_to_del_timer_sync
returns a special code (-1) if the timer couldn't be deleted because it
is currently running, whereas del_timer doesn't check this.

Furthermore, the "_sync" in the name suggests that 
try_to_del_timer_sync will wait until a running timer has finished, 
which it clearly does not do.

Despite these facts, the kerneldoc for try_to_del_timer_sync states 
that it must not be called in interrupt context.  Why not?  Isn't that
advice simply wrong?

With this in mind, would there be any objection if I renamed it to 
try_to_del_timer(), removed the comment forbidding it to be used in 
interrupt context, and made it available even on non-SMP builds?

Alan Stern

P.S.: The only other difference is that del_timer calls
timer_stats_timer_clear_start_info.  Why doesn't try_to_del_timer_sync
do the same thing?

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