LinuxLists.cc - [PATCH] mac80211: Prevent starting of hw scan if it is already in progress

2010-04-08 11:28:04

Subject: [PATCH] mac80211: Prevent starting of hw scan if it is already in progress

Added checking of status of scanning to ieee80211_scan_work when hw
scanning is used. It is possible to scan_work get executed while scan
has already been started. Previously this has led to a state where, when
the driver returned EBUSY, the stack aborted scan while hw was left
scanning. That has caused warnings from ieee80211_scan_completed when
the scan actually has been completed.

Signed-off-by: Teemu Paasikivi <[email protected]>
---
net/mac80211/ieee80211_i.h | 1 +
net/mac80211/scan.c | 8 +++++++-
2 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 741fb8b..1d14f7c 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -756,6 +756,7 @@ struct ieee80211_local {
/* Scanning and BSS list */
struct mutex scan_mtx;
unsigned long scanning;
+ bool hw_scan_continue;
struct cfg80211_ssid scan_ssid;
struct cfg80211_scan_request *int_scan_req;
struct cfg80211_scan_request *scan_req, *hw_scan_req;
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 75a8597..4e4bad0 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -265,12 +265,14 @@ void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)

was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
+ local->hw_scan_continue = true;
ieee80211_queue_delayed_work(&local->hw,
&local->scan_work, 0);
mutex_unlock(&local->scan_mtx);
return;
}

+ local->hw_scan_continue = false;
kfree(local->hw_scan_req);
local->hw_scan_req = NULL;

@@ -652,7 +654,11 @@ void ieee80211_scan_work(struct work_struct *work)
}

if (local->hw_scan_req) {
- int rc = drv_hw_scan(local, local->hw_scan_req);
+ int rc = 0;
+
+ if (!local->scanning || local->hw_scan_continue)
+ rc = drv_hw_scan(local, local->hw_scan_req);
+
mutex_unlock(&local->scan_mtx);
if (rc)
ieee80211_scan_completed(&local->hw, true);
--
1.5.6.3

2010-04-09 07:44:21

by Johannes Berg

[permalink] [raw]

Subject: Re: [PATCH] mac80211: Prevent starting of hw scan if it is already in progress

On Thu, 2010-04-08 at 14:23 +0300, Teemu Paasikivi wrote:
> Added checking of status of scanning to ieee80211_scan_work when hw
> scanning is used. It is possible to scan_work get executed while scan
> has already been started. Previously this has led to a state where, when
> the driver returned EBUSY, the stack aborted scan while hw was left
> scanning. That has caused warnings from ieee80211_scan_completed when
> the scan actually has been completed.
>
> Signed-off-by: Teemu Paasikivi <[email protected]>
> ---
> net/mac80211/ieee80211_i.h | 1 +
> net/mac80211/scan.c | 8 +++++++-
> 2 files changed, 8 insertions(+), 1 deletions(-)
>
> diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
> index 741fb8b..1d14f7c 100644
> --- a/net/mac80211/ieee80211_i.h
> +++ b/net/mac80211/ieee80211_i.h
> @@ -756,6 +756,7 @@ struct ieee80211_local {
> /* Scanning and BSS list */
> struct mutex scan_mtx;
> unsigned long scanning;
> + bool hw_scan_continue;
> struct cfg80211_ssid scan_ssid;
> struct cfg80211_scan_request *int_scan_req;
> struct cfg80211_scan_request *scan_req, *hw_scan_req;
> diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
> index 75a8597..4e4bad0 100644
> --- a/net/mac80211/scan.c
> +++ b/net/mac80211/scan.c
> @@ -265,12 +265,14 @@ void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
>
> was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
> if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
> + local->hw_scan_continue = true;
> ieee80211_queue_delayed_work(&local->hw,
> &local->scan_work, 0);
> mutex_unlock(&local->scan_mtx);
> return;
> }
>
> + local->hw_scan_continue = false;
> kfree(local->hw_scan_req);
> local->hw_scan_req = NULL;
>
> @@ -652,7 +654,11 @@ void ieee80211_scan_work(struct work_struct *work)
> }
>
> if (local->hw_scan_req) {
> - int rc = drv_hw_scan(local, local->hw_scan_req);
> + int rc = 0;
> +
> + if (!local->scanning || local->hw_scan_continue)
> + rc = drv_hw_scan(local, local->hw_scan_req);
> +

So Luis says he can make something similar happen with SW scan, where we
call drv_sw_scan_start twice?

johannes

2010-04-09 08:31:01

by Luis R. Rodriguez

[permalink] [raw]

Subject: Re: [PATCH] mac80211: Prevent starting of hw scan if it is already in progress

On Fri, Apr 9, 2010 at 12:44 AM, Johannes Berg
<[email protected]> wrote:
> On Thu, 2010-04-08 at 14:23 +0300, Teemu Paasikivi wrote:
>> Added checking of status of scanning to ieee80211_scan_work when hw
>> scanning is used. It is possible to scan_work get executed while scan
>> has already been started. Previously this has led to a state where, when
>> the driver returned EBUSY, the stack aborted scan while hw was left
>> scanning. That has caused warnings from ieee80211_scan_completed when
>> the scan actually has been completed.
>>
>> Signed-off-by: Teemu Paasikivi <[email protected]>
>> ---
>> net/mac80211/ieee80211_i.h | 1 +
>> net/mac80211/scan.c | 8 +++++++-
>> 2 files changed, 8 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
>> index 741fb8b..1d14f7c 100644
>> --- a/net/mac80211/ieee80211_i.h
>> +++ b/net/mac80211/ieee80211_i.h
>> @@ -756,6 +756,7 @@ struct ieee80211_local {
>> /* Scanning and BSS list */
>> struct mutex scan_mtx;
>> unsigned long scanning;
>> + bool hw_scan_continue;
>> struct cfg80211_ssid scan_ssid;
>> struct cfg80211_scan_request *int_scan_req;
>> struct cfg80211_scan_request *scan_req, *hw_scan_req;
>> diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
>> index 75a8597..4e4bad0 100644
>> --- a/net/mac80211/scan.c
>> +++ b/net/mac80211/scan.c
>> @@ -265,12 +265,14 @@ void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
>>
>> was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
>> if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
>> + local->hw_scan_continue = true;
>> ieee80211_queue_delayed_work(&local->hw,
>> &local->scan_work, 0);
>> mutex_unlock(&local->scan_mtx);
>> return;
>> }
>>
>> + local->hw_scan_continue = false;
>> kfree(local->hw_scan_req);
>> local->hw_scan_req = NULL;
>>
>> @@ -652,7 +654,11 @@ void ieee80211_scan_work(struct work_struct *work)
>> }
>>
>> if (local->hw_scan_req) {
>> - int rc = drv_hw_scan(local, local->hw_scan_req);
>> + int rc = 0;
>> +
>> + if (!local->scanning || local->hw_scan_continue)
>> + rc = drv_hw_scan(local, local->hw_scan_req);
>> +
>
> So Luis says he can make something similar happen with SW scan, where we
> call drv_sw_scan_start twice?

Right, see the mac80211_hswim patch, it is possible.

Luis