Re: [linux-pm] runtime PM usage_count during driver_probe_device()?
From: Alan Stern <stern@rowland.harvard.edu>
Date: 2011-07-01 15:25:57
On Fri, 1 Jul 2011, Kevin Hilman wrote:
OK, so the ->probe() part has been explained and makes sense, but I would expect ->remove() to be similarily protected (as the documentation states.) But that is not the case. Is that a bug? If so, patch below makes the code match the documentation.
I suspect it is a bug, but it's hard to be sure. It's so _blatantly_ wrong that it looks like it was done deliberately.
quoted hunk ↗ jump to hunk
Kevin From eef73ab2feb203bacb57dc35862f2a9969b61593 Mon Sep 17 00:00:00 2001 From: Kevin Hilman <redacted> Date: Fri, 1 Jul 2011 07:37:47 -0700 Subject: [PATCH] driver core: prevent runtime PM races with ->remove() Runtime PM Documentation states that the runtime PM usage count is incremented during driver ->probe() and ->remove(). This is designed to prevent driver runtime PM races with subsystems which may initiate runtime PM transitions before during and after drivers are loaded. Current code increments the usage_count during ->probe() but not during ->remove(). This patch fixes the ->remove() part and makes the code match the documentation. Signed-off-by: Kevin Hilman <redacted> --- drivers/base/dd.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-)diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 6658da7..47e079d 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c@@ -329,13 +329,13 @@ static void __device_release_driver(struct device *dev) blocking_notifier_call_chain(&dev->bus->p->bus_notifier, BUS_NOTIFY_UNBIND_DRIVER, dev); - - pm_runtime_put_sync(dev); - if (dev->bus && dev->bus->remove) dev->bus->remove(dev); else if (drv->remove) drv->remove(dev); + + pm_runtime_put_sync(dev); + devres_release_all(dev); dev->driver = NULL; klist_remove(&dev->p->knode_driver);
To be safer, the put_sync() call should be moved down here. Or maybe even after the blocking_notifier_call_chain() that occurs here. Alan Stern