Re: [PATCH v2 4/9] clocksource/cadence_ttc: Use enable/disable_irq

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On 11/27/2013 02:04 AM, Soren Brinkmann wrote:
To ensure that the timer interrupt is properly enabled/disabled across
the whole CPU cluster use enable/disable_irq() instead of
local_irq_disable().

Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx>
---
  drivers/clocksource/cadence_ttc_timer.c | 6 ++----
  1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/cadence_ttc_timer.c b/drivers/clocksource/cadence_ttc_timer.c
index a92350b55d32..246d018d1e63 100644
--- a/drivers/clocksource/cadence_ttc_timer.c
+++ b/drivers/clocksource/cadence_ttc_timer.c
@@ -322,18 +322,16 @@ static int ttc_rate_change_clockevent_cb(struct notifier_block *nb,
  	switch (event) {
  	case POST_RATE_CHANGE:
  	{
-		unsigned long flags;
-
  		/*
  		 * clockevents_update_freq should be called with IRQ disabled on
  		 * the CPU the timer provides events for. The timer we use is
  		 * common to both CPUs, not sure if we need to run on both
  		 * cores.
  		 */
-		local_irq_save(flags);
+		disable_irq(ttcce->ce.irq);
  		clockevents_update_freq(&ttcce->ce,
  				ndata->new_rate / PRESCALE);
-		local_irq_restore(flags);
+		enable_irq(ttcce->ce.irq);

  		/* update cached frequency */
  		ttc->freq = ndata->new_rate;


I am worried about the 'disable_irq' function calling 'synchronize_irq'. Isn't possible to deadlock with the ondemand cpufreq governor ? I added Viresh in Cc, he knows better than me the code path.

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