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SubjectRe: [PATCH 13/62] firewire: convert to idr_alloc()
On Feb 02 Tejun Heo wrote:
> Convert to the much saner new idr interface.
>
> Only compile tested.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
> Cc: linux1394-devel@lists.sourceforge.net
> ---
> This patch depends on an earlier idr changes and I think it would be
> best to route these together through -mm. Please holler if there's
> any objection. Thanks.
>
> drivers/firewire/core-cdev.c | 16 +++++++---------
> drivers/firewire/core-device.c | 5 ++---
> 2 files changed, 9 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
> index 68c3138..46a1f88 100644
> --- a/drivers/firewire/core-cdev.c
> +++ b/drivers/firewire/core-cdev.c
> @@ -490,24 +490,22 @@ static int add_client_resource(struct client *client,
> unsigned long flags;
> int ret;
>
> - retry:
> - if (idr_pre_get(&client->resource_idr, gfp_mask) == 0)
> - return -ENOMEM;
> -
> + idr_preload(gfp_mask);
> spin_lock_irqsave(&client->lock, flags);
> +
> if (client->in_shutdown)
> ret = -ECANCELED;
> else
> - ret = idr_get_new(&client->resource_idr, resource,
> - &resource->handle);
> + ret = idr_alloc(&client->resource_idr, resource, 0, 0,
> + GFP_NOWAIT);
> if (ret >= 0) {
> + resource->handle = ret;
> client_get(client);
> schedule_if_iso_resource(resource);
> }
> - spin_unlock_irqrestore(&client->lock, flags);
>
> - if (ret == -EAGAIN)
> - goto retry;
> + spin_unlock_irqrestore(&client->lock, flags);
> + idr_preload_end();
>
> return ret < 0 ? ret : 0;
> }

Most of the add_client_resource() callers are process context (user
process doing an ioctl()), and for them this is going to work fine. But
one caller is tasklet context (firewire-ohci's asynchronous reception DMA
IRQ handler "bottom half").

The kerneldoc comment in 05/62 "idr: implement idr_preload[_end]() and
idr_alloc()" tells me that idr_preload and idr_preload_end must be used in
process context only. Can it work in tasklet context regardless? I am
not entirely sure from looking at the implementation.

> diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
> index 3873d53..c137de6 100644
> --- a/drivers/firewire/core-device.c
> +++ b/drivers/firewire/core-device.c
> @@ -1017,13 +1017,12 @@ static void fw_device_init(struct work_struct *work)
>
> fw_device_get(device);
> down_write(&fw_device_rwsem);
> - ret = idr_pre_get(&fw_device_idr, GFP_KERNEL) ?
> - idr_get_new(&fw_device_idr, device, &minor) :
> - -ENOMEM;
> + ret = idr_alloc(&fw_device_idr, device, 0, 0, GFP_KERNEL);
> up_write(&fw_device_rwsem);
>
> if (ret < 0)
> goto error;
> + minor = ret;
>
> device->device.bus = &fw_bus_type;
> device->device.type = &fw_device_type;

This hunk is OK, of course.
--
Stefan Richter
-=====-===-= --=- ---==
http://arcgraph.de/sr/


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