From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
To: Johannes Berg <johannes@sipsolutions.net>, pkshih@realtek.com
Cc: linux-wireless@vger.kernel.org, tony0620emma@gmail.com,
kvalo@codeaurora.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, Neo Jou <neojou@gmail.com>,
Jernej Skrabec <jernej.skrabec@gmail.com>
Subject: Re: [PATCH RFC v1 3/7] rtw88: Use rtw_iterate_stas where the iterator reads or writes registers
Date: Sun, 25 Jul 2021 23:51:09 +0200 [thread overview]
Message-ID: <CAFBinCAzoPmtvH1Wn9dY4pFsERQ5N+0xXRG=UB1eEGe_qTf+6w@mail.gmail.com> (raw)
In-Reply-To: <27d8246ef3c9755b3e6e908188ca36f7b0fab3fc.camel@sipsolutions.net>
[-- Attachment #1: Type: text/plain, Size: 2308 bytes --]
Hi Johannes, Hi Ping-Ke,
On Mon, Jul 19, 2021 at 8:36 AM Johannes Berg <johannes@sipsolutions.net> wrote:
>
> On Sat, 2021-07-17 at 22:40 +0200, Martin Blumenstingl wrote:
> >
> > --- a/drivers/net/wireless/realtek/rtw88/mac80211.c
> > +++ b/drivers/net/wireless/realtek/rtw88/mac80211.c
> > @@ -721,7 +721,7 @@ static void rtw_ra_mask_info_update(struct rtw_dev *rtwdev,
> > br_data.rtwdev = rtwdev;
> > br_data.vif = vif;
> > br_data.mask = mask;
> > - rtw_iterate_stas_atomic(rtwdev, rtw_ra_mask_info_update_iter, &br_data);
> > + rtw_iterate_stas(rtwdev, rtw_ra_mask_info_update_iter, &br_data);
>
> And then you pretty much immediately break that invariant here, namely
> that you're calling this within the set_bitrate_mask() method called by
> mac80211.
you are right, I was not aware of this
> That's not actually fundamentally broken today, but it does *severely*
> restrict what we can do in mac80211 wrt. locking, and I really don't
> want to keep the dozen or so locks forever, this needs simplification
> because clearly we don't even know what should be under what lock.
To me it's also not clear what the goal of the whole locking is.
The lock in ieee80211_iterate_stations_atomic is obviously for the
mac80211-internal state-machine
But I *believe* that there's a second purpose (rtw88 specific) -
here's my understanding of that part:
- rtw_sta_info contains a "mac_id" which is an identifier for a
specific station used by the rtw88 driver and is shared with the
firmware
- rtw_ops_sta_{add,remove} uses rtwdev->mutex to protect the rtw88
side of this "mac_id" identifier
- (for some reason rtw_update_sta_info doesn't use rtwdev->mutex)
So now I am wondering if the ieee80211_iterate_stations_atomic lock is
also used to protect any modifications to rtw_sta_info.
Ping-Ke, I am wondering if the attached patch (untested - to better
demonstrate what I want to say) would:
- allow us to move the register write outside of
ieee80211_iterate_stations_atomic
- mean we can keep ieee80211_iterate_stations_atomic (instead of the
non-atomic variant)
- protect the code managing the "mac_id" with rtwdev->mutex consistently
> The other cases look OK, it's being called from outside contexts
> (wowlan, etc.)
Thanks for reviewing this Johannes!
Best regards,
Martin
[-- Attachment #2: rtw_update_sta_info-outside-rtw_iterate_stas_atomic.patch --]
[-- Type: text/x-patch, Size: 1505 bytes --]
diff --git a/drivers/net/wireless/realtek/rtw88/mac80211.c b/drivers/net/wireless/realtek/rtw88/mac80211.c
index 7650a1ca0e9e..be39c6d0ee31 100644
--- a/drivers/net/wireless/realtek/rtw88/mac80211.c
+++ b/drivers/net/wireless/realtek/rtw88/mac80211.c
@@ -689,6 +689,8 @@ struct rtw_iter_bitrate_mask_data {
struct rtw_dev *rtwdev;
struct ieee80211_vif *vif;
const struct cfg80211_bitrate_mask *mask;
+ unsigned int num_si;
+ struct rtw_sta_info *si[RTW_MAX_MAC_ID_NUM];
};
static void rtw_ra_mask_info_update_iter(void *data, struct ieee80211_sta *sta)
@@ -709,7 +711,8 @@ static void rtw_ra_mask_info_update_iter(void *data, struct ieee80211_sta *sta)
}
si->use_cfg_mask = true;
- rtw_update_sta_info(br_data->rtwdev, si);
+
+ br_data->si[br_data->num_si++] = si;
}
static void rtw_ra_mask_info_update(struct rtw_dev *rtwdev,
@@ -717,11 +720,20 @@ static void rtw_ra_mask_info_update(struct rtw_dev *rtwdev,
const struct cfg80211_bitrate_mask *mask)
{
struct rtw_iter_bitrate_mask_data br_data;
+ unsigned int i;
+
+ mutex_lock(&rtwdev->mutex);
br_data.rtwdev = rtwdev;
br_data.vif = vif;
br_data.mask = mask;
- rtw_iterate_stas(rtwdev, rtw_ra_mask_info_update_iter, &br_data);
+ br_data.num_si = 0;
+ rtw_iterate_stas_atomic(rtwdev, rtw_ra_mask_info_update_iter, &br_data);
+
+ for (i = 0; i < br_data.num_si; i++)
+ rtw_update_sta_info(rtwdev, br_data.si[i]);
+
+ mutex_unlock(&rtwdev->mutex);
}
static int rtw_ops_set_bitrate_mask(struct ieee80211_hw *hw,
next prev parent reply other threads:[~2021-07-25 21:51 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-17 20:40 [PATCH RFC v1 0/7] rtw88: prepare locking for SDIO support Martin Blumenstingl
2021-07-17 20:40 ` [PATCH RFC v1 1/7] mac80211: Add stations iterator where the iterator function may sleep Martin Blumenstingl
2021-07-19 5:46 ` Pkshih
2021-07-19 6:30 ` Johannes Berg
2021-07-17 20:40 ` [PATCH RFC v1 2/7] rtw88: Use rtw_iterate_vifs where the iterator reads or writes registers Martin Blumenstingl
2021-07-19 5:47 ` Pkshih
2021-07-25 21:31 ` Martin Blumenstingl
2021-07-26 7:22 ` Pkshih
2021-07-17 20:40 ` [PATCH RFC v1 3/7] rtw88: Use rtw_iterate_stas " Martin Blumenstingl
2021-07-19 6:36 ` Johannes Berg
2021-07-25 21:51 ` Martin Blumenstingl [this message]
2021-07-26 7:22 ` Pkshih
2021-08-09 20:00 ` Johannes Berg
2021-07-17 20:40 ` [PATCH RFC v1 4/7] rtw88: Replace usage of rtw_iterate_keys_rcu() with rtw_iterate_keys() Martin Blumenstingl
2021-07-17 20:40 ` [PATCH RFC v1 5/7] rtw88: Configure the registers from rtw_bf_assoc() outside the RCU lock Martin Blumenstingl
2021-07-19 5:47 ` Pkshih
2021-07-25 21:36 ` Martin Blumenstingl
2021-07-26 7:22 ` Pkshih
2021-07-17 20:40 ` [PATCH RFC v1 6/7] rtw88: hci: Convert rf_lock from a spinlock to a mutex Martin Blumenstingl
2021-07-17 20:40 ` [PATCH RFC v1 7/7] rtw88: fw: Convert h2c.lock " Martin Blumenstingl
2021-07-19 5:52 ` [PATCH RFC v1 0/7] rtw88: prepare locking for SDIO support Pkshih
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