From: Kalle Valo <kvalo@codeaurora.org>
To: "Michael Büsch" <m@bues.ch>
Cc: Jia-Ju Bai <baijiaju1990@163.com>,
netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
b43-dev@lists.infradead.org, linux-kernel@vger.kernel.org,
Larry.Finger@lwfinger.net
Subject: Re: [PATCH] b43legacy: Fix a sleep-in-atomic bug in b43legacy_op_bss_info_changed
Date: Thu, 01 Jun 2017 07:27:20 +0300 [thread overview]
Message-ID: <878tlcmixj.fsf@kamboji.qca.qualcomm.com> (raw)
In-Reply-To: <20170531173107.25eeda48@wiggum> ("Michael \=\?utf-8\?Q\?B\=C3\=BCs\?\= \=\?utf-8\?Q\?ch\=22's\?\= message of "Wed, 31 May 2017 17:32:15 +0200")
Michael B=C3=BCsch <m@bues.ch> writes:
>> > --- a/drivers/net/wireless/broadcom/b43legacy/main.c
>> > +++ b/drivers/net/wireless/broadcom/b43legacy/main.c
>> > @@ -2859,7 +2859,9 @@ static void b43legacy_op_bss_info_changed(struct=
ieee80211_hw *hw,
>> > b43legacy_write32(dev, B43legacy_MMIO_GEN_IRQ_MASK, 0);
>> >=20=20
>> > if (changed & BSS_CHANGED_BSSID) {
>> > + spin_unlock_irqrestore(&wl->irq_lock, flags);
>> > b43legacy_synchronize_irq(dev);
>> > + spin_lock_irqsave(&wl->irq_lock, flags);=20=20
>>=20
>> To me this looks like a fragile workaround and not a real fix. You can
>> easily add new race conditions with releasing the lock like this.
>>=20
>
>
> I think releasing the lock possibly is fine. It certainly is better than
> sleeping with a lock held.
Sure, but IMHO in general I think the practise of releasing the lock
like this in a middle of function is dangerous as one can easily miss
that upper and lower halves of the function are not actually atomic
anymore. And in this case that it's under a conditional makes it even
worse.
--=20
Kalle Valo
WARNING: multiple messages have this Message-ID (diff)
From: Kalle Valo <kvalo@codeaurora.org>
To: "Michael Büsch" <m@bues.ch>
Cc: Jia-Ju Bai <baijiaju1990@163.com>,
netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
b43-dev@lists.infradead.org, linux-kernel@vger.kernel.org,
Larry.Finger@lwfinger.net
Subject: Re: [PATCH] b43legacy: Fix a sleep-in-atomic bug in b43legacy_op_bss_info_changed
Date: Thu, 01 Jun 2017 07:27:20 +0300 [thread overview]
Message-ID: <878tlcmixj.fsf@kamboji.qca.qualcomm.com> (raw)
In-Reply-To: <20170531173107.25eeda48@wiggum> ("Michael \=\?utf-8\?Q\?B\=C3\=BCs\?\= \=\?utf-8\?Q\?ch\=22's\?\= message of "Wed, 31 May 2017 17:32:15 +0200")
Michael Büsch <m@bues.ch> writes:
>> > --- a/drivers/net/wireless/broadcom/b43legacy/main.c
>> > +++ b/drivers/net/wireless/broadcom/b43legacy/main.c
>> > @@ -2859,7 +2859,9 @@ static void b43legacy_op_bss_info_changed(struct ieee80211_hw *hw,
>> > b43legacy_write32(dev, B43legacy_MMIO_GEN_IRQ_MASK, 0);
>> >
>> > if (changed & BSS_CHANGED_BSSID) {
>> > + spin_unlock_irqrestore(&wl->irq_lock, flags);
>> > b43legacy_synchronize_irq(dev);
>> > + spin_lock_irqsave(&wl->irq_lock, flags);
>>
>> To me this looks like a fragile workaround and not a real fix. You can
>> easily add new race conditions with releasing the lock like this.
>>
>
>
> I think releasing the lock possibly is fine. It certainly is better than
> sleeping with a lock held.
Sure, but IMHO in general I think the practise of releasing the lock
like this in a middle of function is dangerous as one can easily miss
that upper and lower halves of the function are not actually atomic
anymore. And in this case that it's under a conditional makes it even
worse.
--
Kalle Valo
WARNING: multiple messages have this Message-ID (diff)
From: Kalle Valo <kvalo@codeaurora.org>
To: "Michael Büsch" <m@bues.ch>
Cc: Jia-Ju Bai <baijiaju1990@163.com>,
netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
b43-dev@lists.infradead.org, linux-kernel@vger.kernel.org,
Larry.Finger@lwfinger.net
Subject: [PATCH] b43legacy: Fix a sleep-in-atomic bug in b43legacy_op_bss_info_changed
Date: Thu, 01 Jun 2017 07:27:20 +0300 [thread overview]
Message-ID: <878tlcmixj.fsf@kamboji.qca.qualcomm.com> (raw)
In-Reply-To: <20170531173107.25eeda48@wiggum> ("Michael \=\?utf-8\?Q\?B\=C3\=BCs\?\= \=\?utf-8\?Q\?ch\=22's\?\= message of "Wed, 31 May 2017 17:32:15 +0200")
Michael B?sch <m@bues.ch> writes:
>> > --- a/drivers/net/wireless/broadcom/b43legacy/main.c
>> > +++ b/drivers/net/wireless/broadcom/b43legacy/main.c
>> > @@ -2859,7 +2859,9 @@ static void b43legacy_op_bss_info_changed(struct ieee80211_hw *hw,
>> > b43legacy_write32(dev, B43legacy_MMIO_GEN_IRQ_MASK, 0);
>> >
>> > if (changed & BSS_CHANGED_BSSID) {
>> > + spin_unlock_irqrestore(&wl->irq_lock, flags);
>> > b43legacy_synchronize_irq(dev);
>> > + spin_lock_irqsave(&wl->irq_lock, flags);
>>
>> To me this looks like a fragile workaround and not a real fix. You can
>> easily add new race conditions with releasing the lock like this.
>>
>
>
> I think releasing the lock possibly is fine. It certainly is better than
> sleeping with a lock held.
Sure, but IMHO in general I think the practise of releasing the lock
like this in a middle of function is dangerous as one can easily miss
that upper and lower halves of the function are not actually atomic
anymore. And in this case that it's under a conditional makes it even
worse.
--
Kalle Valo
next prev parent reply other threads:[~2017-06-01 4:27 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-31 10:09 [PATCH] b43legacy: Fix a sleep-in-atomic bug in b43legacy_op_bss_info_changed Jia-Ju Bai
2017-05-31 10:26 ` Kalle Valo
2017-05-31 10:26 ` Kalle Valo
2017-05-31 12:15 ` Arend van Spriel
2017-05-31 12:15 ` Arend van Spriel
2017-05-31 15:32 ` Michael Büsch
2017-05-31 15:32 ` Michael Büsch
2017-06-01 0:07 ` Larry Finger
2017-06-01 0:07 ` Larry Finger
2017-06-01 0:07 ` Larry Finger
2017-06-01 1:07 ` Jia-Ju Bai
2017-06-01 1:07 ` Jia-Ju Bai
2017-06-01 1:07 ` Jia-Ju Bai
2017-06-01 5:31 ` Michael Büsch
2017-06-01 5:31 ` Michael Büsch
2017-06-01 4:27 ` Kalle Valo [this message]
2017-06-01 4:27 ` Kalle Valo
2017-06-01 4:27 ` Kalle Valo
2017-06-01 5:29 ` Michael Büsch
2017-06-01 5:29 ` Michael Büsch
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