Re: [PATCH 6/7] mwifiex: factor out mwifiex_cancel_pending_scan_cmd
Hi Julian,
thanks for your time!
2016-02-25 2:14 GMT+01:00 Julian Calaby :
> Hi Andreas,
>
> On Thu, Feb 25, 2016 at 11:08 AM, Andreas Fenkart wrote:
>> releasing the scan_pending lock in mwifiex_check_next_scan_command
>> is valid, since the lock is taken again, and all nodes removed
>> from the scan_pending queue.
>>
>> Signed-off-by: Andreas Fenkart
>> ---
>> drivers/net/wireless/marvell/mwifiex/cmdevt.c | 43
>> ++
>> drivers/net/wireless/marvell/mwifiex/main.h| 1 +
>> drivers/net/wireless/marvell/mwifiex/scan.c| 23 +++-
>> drivers/net/wireless/marvell/mwifiex/sta_cmdresp.c | 13 +--
>> 4 files changed, 27 insertions(+), 53 deletions(-)
>>
>> diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c
>> b/drivers/net/wireless/marvell/mwifiex/scan.c
>> index 6ddc98b..490d0d1 100644
>> --- a/drivers/net/wireless/marvell/mwifiex/scan.c
>> +++ b/drivers/net/wireless/marvell/mwifiex/scan.c
>> @@ -1920,13 +1910,10 @@ static void mwifiex_check_next_scan_command(struct
>> mwifiex_private *priv)
>> }
>> } else if ((priv->scan_aborting && !priv->scan_request) ||
>>priv->scan_block) {
>> - list_for_each_entry_safe(cmd_node, tmp_node,
>> -&adapter->scan_pending_q, list) {
>> - list_del(&cmd_node->list);
>> - mwifiex_insert_cmd_to_free_q(adapter, cmd_node);
>> - }
>> spin_unlock_irqrestore(&adapter->scan_pending_q_lock, flags);
>>
>> + mwifiex_cancel_pending_scan_cmd(adapter);
>> +
>
> This is creating a "short" window where &adapter->scan_pending_q_lock
> is unlocked here. Is that safe?
>
> You might want to write mwifiex_cancel_pending_scan_cmd() as two
> functions, one which takes the spinlock and calls the other and one
> which does all the work so you can call the latter here without that
> window where ..._q_lock is unlocked.
I added this comment to the description of the updated patch, that I
will send out shortly:
Releasing the scan_pending lock in mwifiex_check_next_scan_command
introduces a short window where pending scan commands can be removed
or added before removing them all in mwifiex_cancel_pending_scan_cmd.
I think this is safe, since the worst thing to happen is that a
pending scan cmd is removed by the command handler. Adding new scan
commands is not possible while one is pending, see scan_processing.
Since all commands are removed from the queue anyway, we don't care if
some commands are removed by a different code path earlier, the final
state remains the same.
I assume, that the critical section needed for the check has been
extended over clearing the pending scan queue, out of convenience. The
lock was already held and releasing it first just to grab it again was
more work. It doesn't seem to be necessary because of concurrency.
Thanks,
Andi
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Re: [PATCH 6/7] mwifiex: factor out mwifiex_cancel_pending_scan_cmd
Hi Andreas,
On Thu, Feb 25, 2016 at 11:08 AM, Andreas Fenkart wrote:
> releasing the scan_pending lock in mwifiex_check_next_scan_command
> is valid, since the lock is taken again, and all nodes removed
> from the scan_pending queue.
>
> Signed-off-by: Andreas Fenkart
> ---
> drivers/net/wireless/marvell/mwifiex/cmdevt.c | 43
> ++
> drivers/net/wireless/marvell/mwifiex/main.h| 1 +
> drivers/net/wireless/marvell/mwifiex/scan.c| 23 +++-
> drivers/net/wireless/marvell/mwifiex/sta_cmdresp.c | 13 +--
> 4 files changed, 27 insertions(+), 53 deletions(-)
>
> diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c
> b/drivers/net/wireless/marvell/mwifiex/scan.c
> index 6ddc98b..490d0d1 100644
> --- a/drivers/net/wireless/marvell/mwifiex/scan.c
> +++ b/drivers/net/wireless/marvell/mwifiex/scan.c
> @@ -1920,13 +1910,10 @@ static void mwifiex_check_next_scan_command(struct
> mwifiex_private *priv)
> }
> } else if ((priv->scan_aborting && !priv->scan_request) ||
>priv->scan_block) {
> - list_for_each_entry_safe(cmd_node, tmp_node,
> -&adapter->scan_pending_q, list) {
> - list_del(&cmd_node->list);
> - mwifiex_insert_cmd_to_free_q(adapter, cmd_node);
> - }
> spin_unlock_irqrestore(&adapter->scan_pending_q_lock, flags);
>
> + mwifiex_cancel_pending_scan_cmd(adapter);
> +
This is creating a "short" window where &adapter->scan_pending_q_lock
is unlocked here. Is that safe?
You might want to write mwifiex_cancel_pending_scan_cmd() as two
functions, one which takes the spinlock and calls the other and one
which does all the work so you can call the latter here without that
window where ..._q_lock is unlocked.
Thanks,
--
Julian Calaby
Email: julian.cal...@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/
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[PATCH 6/7] mwifiex: factor out mwifiex_cancel_pending_scan_cmd
releasing the scan_pending lock in mwifiex_check_next_scan_command
is valid, since the lock is taken again, and all nodes removed
from the scan_pending queue.
Signed-off-by: Andreas Fenkart
---
drivers/net/wireless/marvell/mwifiex/cmdevt.c | 43 ++
drivers/net/wireless/marvell/mwifiex/main.h| 1 +
drivers/net/wireless/marvell/mwifiex/scan.c| 23 +++-
drivers/net/wireless/marvell/mwifiex/sta_cmdresp.c | 13 +--
4 files changed, 27 insertions(+), 53 deletions(-)
diff --git a/drivers/net/wireless/marvell/mwifiex/cmdevt.c
b/drivers/net/wireless/marvell/mwifiex/cmdevt.c
index cb25aa7..61426b3 100644
--- a/drivers/net/wireless/marvell/mwifiex/cmdevt.c
+++ b/drivers/net/wireless/marvell/mwifiex/cmdevt.c
@@ -991,6 +991,23 @@ mwifiex_cmd_timeout_func(unsigned long function_context)
adapter->if_ops.card_reset(adapter);
}
+void
+mwifiex_cancel_pending_scan_cmd(struct mwifiex_adapter *adapter)
+{
+ struct cmd_ctrl_node *cmd_node = NULL, *tmp_node;
+ unsigned long flags;
+
+ /* Cancel all pending scan command */
+ spin_lock_irqsave(&adapter->scan_pending_q_lock, flags);
+ list_for_each_entry_safe(cmd_node, tmp_node,
+&adapter->scan_pending_q, list) {
+ list_del(&cmd_node->list);
+ cmd_node->wait_q_enabled = false;
+ mwifiex_insert_cmd_to_free_q(adapter, cmd_node);
+ }
+ spin_unlock_irqrestore(&adapter->scan_pending_q_lock, flags);
+}
+
/*
* This function cancels all the pending commands.
*
@@ -1029,16 +1046,7 @@ mwifiex_cancel_all_pending_cmd(struct mwifiex_adapter
*adapter)
spin_unlock_irqrestore(&adapter->cmd_pending_q_lock, flags);
spin_unlock_irqrestore(&adapter->mwifiex_cmd_lock, cmd_flags);
- /* Cancel all pending scan command */
- spin_lock_irqsave(&adapter->scan_pending_q_lock, flags);
- list_for_each_entry_safe(cmd_node, tmp_node,
-&adapter->scan_pending_q, list) {
- list_del(&cmd_node->list);
-
- cmd_node->wait_q_enabled = false;
- mwifiex_insert_cmd_to_free_q(adapter, cmd_node);
- }
- spin_unlock_irqrestore(&adapter->scan_pending_q_lock, flags);
+ mwifiex_cancel_pending_scan_cmd(adapter);
if (adapter->scan_processing) {
spin_lock_irqsave(&adapter->mwifiex_cmd_lock, cmd_flags);
@@ -1070,9 +1078,8 @@ mwifiex_cancel_all_pending_cmd(struct mwifiex_adapter
*adapter)
void
mwifiex_cancel_pending_ioctl(struct mwifiex_adapter *adapter)
{
- struct cmd_ctrl_node *cmd_node = NULL, *tmp_node = NULL;
+ struct cmd_ctrl_node *cmd_node = NULL;
unsigned long cmd_flags;
- unsigned long scan_pending_q_flags;
struct mwifiex_private *priv;
int i;
@@ -1094,17 +1101,7 @@ mwifiex_cancel_pending_ioctl(struct mwifiex_adapter
*adapter)
mwifiex_recycle_cmd_node(adapter, cmd_node);
}
- /* Cancel all pending scan command */
- spin_lock_irqsave(&adapter->scan_pending_q_lock,
- scan_pending_q_flags);
- list_for_each_entry_safe(cmd_node, tmp_node,
-&adapter->scan_pending_q, list) {
- list_del(&cmd_node->list);
- cmd_node->wait_q_enabled = false;
- mwifiex_insert_cmd_to_free_q(adapter, cmd_node);
- }
- spin_unlock_irqrestore(&adapter->scan_pending_q_lock,
- scan_pending_q_flags);
+ mwifiex_cancel_pending_scan_cmd(adapter);
if (adapter->scan_processing) {
spin_lock_irqsave(&adapter->mwifiex_cmd_lock, cmd_flags);
diff --git a/drivers/net/wireless/marvell/mwifiex/main.h
b/drivers/net/wireless/marvell/mwifiex/main.h
index 2f7f478..f71f894 100644
--- a/drivers/net/wireless/marvell/mwifiex/main.h
+++ b/drivers/net/wireless/marvell/mwifiex/main.h
@@ -1043,6 +1043,7 @@ int mwifiex_alloc_cmd_buffer(struct mwifiex_adapter
*adapter);
int mwifiex_free_cmd_buffer(struct mwifiex_adapter *adapter);
void mwifiex_cancel_all_pending_cmd(struct mwifiex_adapter *adapter);
void mwifiex_cancel_pending_ioctl(struct mwifiex_adapter *adapter);
+void mwifiex_cancel_pending_scan_cmd(struct mwifiex_adapter *adapter);
void mwifiex_insert_cmd_to_free_q(struct mwifiex_adapter *adapter,
struct cmd_ctrl_node *cmd_node);
diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c
b/drivers/net/wireless/marvell/mwifiex/scan.c
index 6ddc98b..490d0d1 100644
--- a/drivers/net/wireless/marvell/mwifiex/scan.c
+++ b/drivers/net/wireless/marvell/mwifiex/scan.c
@@ -563,8 +563,6 @@ mwifiex_scan_channel_list(struct mwifiex_private *priv,
int ret = 0;
struct mwifiex_chan_scan_param_set *tmp_chan_list;
struct mwifiex_chan_scan_param_set *start_chan;
- struct cmd_ctrl_node *cmd_node, *tmp_node;
- unsigned lon
