Re: [PATCH v5.18] ath9k: Properly clear TX status area before reporting to mac80211

[Peter Seiderer <ps.report@gmx.net>]

Hello Toke,

On Sat, 02 Apr 2022 17:11:54 +0200, Toke Høiland-Jørgensen <toke@toke.dk> wrote:

> Peter Seiderer <ps.report@gmx.net> writes:
> 
> > Hello Toke,
> >
> > On Fri, 1 Apr 2022 19:26:57 +0200, Peter Seiderer <ps.report@gmx.net> wrote:
> >  
> >> Hello Toke,
> >> 
> >> On Wed, 30 Mar 2022 18:44:09 +0200, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> >>   
> >> > The ath9k driver was not properly clearing the status area in the
> >> > ieee80211_tx_info struct before reporting TX status to mac80211. Instead,
> >> > it was manually filling in fields, which meant that fields introduced later
> >> > were left as-is.
> >> > 
> >> > Conveniently, mac80211 actually provides a helper to zero out the status
> >> > area, so use that to make sure we zero everything.
> >> > 
> >> > The last commit touching the driver function writing the status information
> >> > seems to have actually been fixing an issue that was also caused by the
> >> > area being uninitialised; but it only added clearing of a single field
> >> > instead of the whole struct. That is now redundant, though, so revert that
> >> > commit and use it as a convenient Fixes tag.
> >> > 
> >> > Fixes: cc591d77aba1 ("ath9k: Make sure to zero status.tx_time before reporting TX status")
> >> > Reported-by: Bagas Sanjaya <bagasdotme@gmail.com>
> >> > Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
> >> > ---
> >> >  drivers/net/wireless/ath/ath9k/xmit.c | 5 ++---
> >> >  1 file changed, 2 insertions(+), 3 deletions(-)
> >> > 
> >> > diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
> >> > index d0caf1de2bde..cbcf96ac303e 100644
> >> > --- a/drivers/net/wireless/ath/ath9k/xmit.c
> >> > +++ b/drivers/net/wireless/ath/ath9k/xmit.c
> >> > @@ -2553,6 +2553,8 @@ static void ath_tx_rc_status(struct ath_softc *sc, struct ath_buf *bf,
> >> >  	struct ath_hw *ah = sc->sc_ah;
> >> >  	u8 i, tx_rateindex;
> >> >  
> >> > +	ieee80211_tx_info_clear_status(tx_info);
> >> > +    
> >> 
> >> As this also clears the status.rates[].count, see include/net/mac80211.h:
> >> 
> >> 1195 static inline void
> >> 1196 ieee80211_tx_info_clear_status(struct ieee80211_tx_info *info)
> >> 1197 {
> >> 1198         int i;
> >> 1199         
> >> 1200         BUILD_BUG_ON(offsetof(struct ieee80211_tx_info, status.rates) !=
> >> 1201                      offsetof(struct ieee80211_tx_info, control.rates));
> >> 1202         BUILD_BUG_ON(offsetof(struct ieee80211_tx_info, status.rates) !=
> >> 1203                      offsetof(struct ieee80211_tx_info, driver_rates));
> >> 1204         BUILD_BUG_ON(offsetof(struct ieee80211_tx_info, status.rates) != 8)     ;       
> >> 1205         /* clear the rate counts */
> >> 1206         for (i = 0; i < IEEE80211_TX_MAX_RATES; i++)
> >> 1207                 info->status.rates[i].count = 0;
> >> 1208         memset_after(&info->status, 0, rates);
> >> 1209 }
> >> 
> >> I would have expected some lines added to restore the count (for the
> >> rates with index < tx_rateindex), e.g. as done in
> >> drivers/net/wireless/ath/ath5k/base.c:
> >> 
> >> 1731         ieee80211_tx_info_clear_status(info);
> >> 1732 
> >> 1733         for (i = 0; i < ts->ts_final_idx; i++) {
> >> 1734                 struct ieee80211_tx_rate *r =
> >> 1735                         &info->status.rates[i];
> >> 1736 
> >> 1737                 r->count = tries[i];
> >> 1738         }
> >> 
> >> In drivers/net/wireless/ath/ath9k/xmit.c this is only done/changed for
> >> the tx_rateindex index (which is often zero in case the first suggested rate
> >> succeeds, but in noisy environment is sometimes > 0)...
> >>   
> >> >  	if (txok)
> >> >  		tx_info->status.ack_signal = ts->ts_rssi;
> >> >  
> >> > @@ -2595,9 +2597,6 @@ static void ath_tx_rc_status(struct ath_softc *sc, struct ath_buf *bf,
> >> >  	}
> >> >  
> >> >  	tx_info->status.rates[)].count = ts->ts_longretry + 1;
> >> > -
> >> > -	/* we report airtime in ath_tx_count_airtime(), don't report twice */
> >> > -	tx_info->status.tx_time = 0;
> >> >  }
> >> >  
> >> >  static void ath_tx_processq(struct ath_softc *sc, struct ath_txq *txq)    
> >> 
> >> 
> >> And from drivers/net/wireless/ath/ath9k/xmit.c:
> >> 
> >> 2592         for (i = tx_rateindex + 1; i < hw->max_rates; i++) {
> >> 2593                 tx_info->status.rates[i].count = 0;
> >> 2594                 tx_info->status.rates[i].idx = -1;
> >> 2595         }
> >> 
> >> Line 2593 can be deleted as status.rates[].count is already zeroed through the
> >> ieee80211_tx_info_clear_status() call...
> >> 
> >> And it should be sufficient to do:
> >> 
> >> 	if (tx_rateindex + 1 < hw->max_rates)
> >> 		tx_info->status.rates[tx_rateindex + 1].idx = -1;
> >> 
> >> Regards,
> >> Peter  
> >
> > And one additional problem found with your patch applied (to 5.16.18), the log
> > get spammed by:
> >
> > [  445.489139] ------------[ cut here ]------------
> > [  445.489150] WARNING: CPU: 0 PID: 8630 at drivers/net/wireless/ath/ath9k/xmit.c:174 ath_tx_complete+0x190/0x1a0 [ath9k]
> > [  445.489178] Modules linked in: ath9k ath9k_common ath9k_hw mac80211 ppp_async ppp_generic slhc xt_u32 xt_TCPMSS xt_tcpmss xt_MASQUERADE iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip6table_filter iptable_filter ip6table_mangle ip6_tables cls_u32 sch_prio qmi_wwan cdc_wdm usbnet qcserial usb_wwan gpio_pca953x xt_tcpudp xt_mark iptable_mangle ip_tables x_tables dummy tqmx86_wdt watchdog i2c_machxo2 gpio_tqmx86 libarc4 ath tqmx86 mfd_core ftdi_sio cfg80211 usbserial nct7802 regmap_i2c [last unloaded: mac80211]
> > [  445.489298] CPU: 0 PID: 8630 Comm: modprobe Tainted: G        W         5.16.18+ #2
> > [  445.489307] Hardware name: TQ-Group TQMxE38M X64/Type2 - Board Product Name, BIOS TQMxE38M.5.4.48.0028.12 01/31/2017
> > [  445.489311] EIP: ath_tx_complete+0x190/0x1a0 [ath9k]
> > [  445.489328] Code: ff 75 e8 68 d7 a1 2c f8 89 55 ec e8 d5 4f e3 ff 8b 45 f0 8b 55 ec 83 c4 10 8b 80 58 0a 00 00 e9 a8 fe ff ff 8d b6 00 00 00 00 <0f> 0b c7 42 68 00 00 00 00 e9 1d ff ff ff 66 90 55 89 e5 57 56 89
> > [  445.489336] EAX: 00000000 EBX: c2e67900 ECX: c23cc040 EDX: c235a980
> > [  445.489342] ESI: c235a888 EDI: c2359860 EBP: c1089e18 ESP: c1089dfc
> > [  445.489348] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 EFLAGS: 00010297
> > [  445.489355] CR0: 80050033 CR2: b7f81000 CR3: 02ec7000 CR4: 001006d0
> > [  445.489362] Call Trace:
> > [  445.489366]  <SOFTIRQ>
> > [  445.489372]  ath_tx_complete_buf+0x100/0x130 [ath9k]
> > [  445.489390]  ath_tx_process_buffer+0x187/0xb40 [ath9k]
> > [  445.489407]  ? resched_curr+0x1d/0xc0
> > [  445.489419]  ? check_preempt_wakeup+0x115/0x250
> > [  445.489429]  ? task_fork_fair+0xc0/0x170
> > [  445.489436]  ? put_prev_task_fair+0x40/0x40
> > [  445.489444]  ? check_preempt_curr+0x62/0x70
> > [  445.489452]  ? __local_bh_enable_ip+0x33/0x80
> > [  445.489460]  ? _raw_spin_unlock_bh+0x13/0x20
> > [  445.489468]  ? ath_txq_unlock_complete+0x5a/0x100 [ath9k]
> > [  445.489485]  ? _raw_spin_unlock_irqrestore+0x16/0x30
> > [  445.489492]  ? try_to_wake_up+0x7c/0x550
> > [  445.489499]  ath_tx_tasklet+0x1de/0x2e0 [ath9k]
> > [  445.489519]  ath9k_tasklet+0x22f/0x330 [ath9k]
> > [  445.489535]  tasklet_action_common.constprop.0+0x89/0xb0
> > [  445.489544]  tasklet_action+0x21/0x30
> > [  445.489551]  __do_softirq+0xc5/0x28b
> > [  445.489559]  ? __entry_text_end+0x4/0x4
> > [  445.489567]  call_on_stack+0x40/0x50
> > [  445.489576]  </SOFTIRQ>
> > [  445.489580]  ? irq_exit_rcu+0x92/0x100
> > [  445.489587]  ? common_interrupt+0x27/0x40
> > [  445.489595]  ? asm_common_interrupt+0x102/0x140
> > [  445.489605] ---[ end trace 5c176b666255bca1 ]---
> > [  445.607206] ------------[ cut here ]------------
> >
> >
> > Could be fixed by the following additional change:
> >
> > --- a/drivers/net/wireless/ath/ath9k/xmit.c
> > +++ b/drivers/net/wireless/ath/ath9k/xmit.c
> > @@ -2511,9 +2511,12 @@ static void ath_tx_rc_status(struct ath_softc *sc, struct ath_buf *bf,
> >         struct ieee80211_hw *hw = sc->hw;
> >         struct ath_hw *ah = sc->sc_ah;
> >         u8 i, tx_rateindex;
> > +       bool is_valid_ack_signal = tx_info->status.is_valid_ack_signal;
> >
> >         ieee80211_tx_info_clear_status(tx_info);
> >
> > +       tx_info->status.is_valid_ack_signal = is_valid_ack_signal;
> > +
> >         if (txok)  
> 
> That doesn't seem right, zeroing is_valid_ack_signal was the whole point
> of the first patch... Something seems off in that backtrace; could you
> try running it through ./scripts/decode_stacktrace.sh please?

Will do (and re-run the test with an fresh compiled kernel as CONFIG_DEBUG_KERNEL
was not set - but need to wait until next week as I need physical access to
the test system for kernel update)...

Regards,
Peter

> 
> -Toke