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ieee1394: node manager causes up to ~3.25s delay in freezing tasks

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The firewire nodemanager function "nodemgr_host_thread" contains a loop
that calls try_to_freeze near the top of the loop, but then delays for
up to 3.25 seconds (plus time to do work) before getting back to the top
of the loop. When starting a cycle post-boot, this doesn't seem to bite,
but it is causing a noticeable delay at boot time, when freezing
processes prior to starting to read the image.

The following patch adds invocation of try_to_freeze to the subloops
that are used in the body of this function. With these additions, the
time to freeze when starting to resume at boot time is virtually zero.
I'm no expert on firewire, and so don't know that we shouldn't check
the return value and jump back to the top of the loop or such like after
being frozen, but I submit it for your consideration.

Signed-off-by: Nigel Cunningham <nigel@tuxonice.net>

The delay until nodemgr freezes was up to 0.25s (plus time for node
probes) in Linux 2.6.27 and older and up to 3.25s (plus ~) since Linux
2.6.28-rc1, hence much more noticeable.

try_to_freeze() without any jump is correct.  The surrounding code in
the respective loops will catch whether another bus reset happens during
the freeze and handle it.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Nigel Cunningham 2008-12-09 22:40:20 +11:00 committed by Stefan Richter
parent 437f2f91d6
commit ec9a13cdbf
1 changed files with 2 additions and 0 deletions
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2
drivers/ieee1394/nodemgr.c
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@ -1685,6 +1685,7 @@ static int nodemgr_host_thread(void *data)
g = get_hpsb_generation(host);
for (i = 0; i < 4 ; i++) {
msleep_interruptible(63);
try_to_freeze();
if (kthread_should_stop())
goto exit;
@ -1725,6 +1726,7 @@ static int nodemgr_host_thread(void *data)
/* Sleep 3 seconds */
for (i = 3000/200; i; i--) {
msleep_interruptible(200);
try_to_freeze();
if (kthread_should_stop())
goto exit;