From: Li Li <[email protected]> Sent: Monday, January 5, 2026 8:39 AM To: Loktionov, Aleksandr <[email protected]> Cc: Nguyen, Anthony L <[email protected]>; Kitszel, Przemyslaw <[email protected]>; David S. Miller <[email protected]>; Jakub Kicinski <[email protected]>; Eric Dumazet <[email protected]>; [email protected]; [email protected]; [email protected]; David Decotigny <[email protected]>; Singhai, Anjali <[email protected]>; Samudrala, Sridhar <[email protected]>; Brian Vazquez <[email protected]>; Tantilov, Emil S <[email protected]> Subject: Re: [Intel-wired-lan] [PATCH v2] idpf: increment completion queue next_to_clean in sw marker wait routine
On Sun, Jan 4, 2026 at 11:19 PM Loktionov, Aleksandr <[email protected]<mailto:[email protected]>> wrote: > -----Original Message----- > From: Intel-wired-lan > <[email protected]<mailto:[email protected]>> > On Behalf > Of Li Li via Intel-wired-lan > Sent: Monday, January 5, 2026 7:47 AM > To: Nguyen, Anthony L > <[email protected]<mailto:[email protected]>>; Kitszel, > Przemyslaw > <[email protected]<mailto:[email protected]>>; David S. > Miller > <[email protected]<mailto:[email protected]>>; Jakub Kicinski > <[email protected]<mailto:[email protected]>>; Eric Dumazet > <[email protected]<mailto:[email protected]>>; > [email protected]<mailto:[email protected]> > Cc: [email protected]<mailto:[email protected]>; > [email protected]<mailto:[email protected]>; David > Decotigny <[email protected]<mailto:[email protected]>>; Singhai, Anjali > <[email protected]<mailto:[email protected]>>; Samudrala, > Sridhar > <[email protected]<mailto:[email protected]>>; Brian > Vazquez <[email protected]<mailto:[email protected]>>; > Tantilov, Emil S > <[email protected]<mailto:[email protected]>>; Li Li > <[email protected]<mailto:[email protected]>> > Subject: [Intel-wired-lan] [PATCH v2] idpf: increment completion queue > next_to_clean in sw marker wait routine > > Currently, in idpf_wait_for_sw_marker_completion(), when an > IDPF_TXD_COMPLT_SW_MARKER packet is found, the routine breaks out of > the for loop and does not increment the next_to_clean counter. This > causes the subsequent NAPI polls to run into the same > IDPF_TXD_COMPLT_SW_MARKER packet again and print out the following: > > [ 23.261341] idpf 0000:05:00.0 eth1: Unknown TX completion type: > 5 > > Instead, we should increment next_to_clean regardless when an > IDPF_TXD_COMPLT_SW_MARKER packet is found. > > Tested: with the patch applied, we do not see the errors above from > NAPI polls anymore. > > Signed-off-by: Li Li <[email protected]<mailto:[email protected]>> > --- > Changes in v2: > - Initialize idpf_tx_queue *target to NULL to suppress the "'target' > uninitialized when 'if' statement is true warning". > > drivers/net/ethernet/intel/idpf/idpf_txrx.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c > b/drivers/net/ethernet/intel/idpf/idpf_txrx.c > index 69bab7187e541..452d0a9e83a4f 100644 > --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c > +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c > @@ -2326,7 +2326,7 @@ void idpf_wait_for_sw_marker_completion(const > struct idpf_tx_queue *txq) > > do { > struct idpf_splitq_4b_tx_compl_desc *tx_desc; > - struct idpf_tx_queue *target; > + struct idpf_tx_queue *target = NULL; Linux kernel is against premature initialization just to silence a compiler. The target variable is dereferenced at idpf_queue_clear(SW_MARKER, target)) but can remain uninitialized if execution jumps to the next: label via a goto before target is assigned. Isn't it? That is correct. When the following if statement (line 2341-2343) evaluates to true: if (FIELD_GET(IDPF_TXD_COMPLQ_COMPL_TYPE_M, ctype_gen) != IDPF_TXD_COMPLT_SW_MARKER) goto next; Then the initialization at line 2346: target = complq->txq_grp->txqs[id]; would be skipped, making "target" uninitialized. Therefore, in this patch, I need to initialize "target" to NULL. The ‘NULL’ target variable can be dereferenced at idpf_queue_clear(SW_MARKER, target)), isn’t it? > u32 ctype_gen, id; > > tx_desc = flow ? &complq->comp[ntc].common : > @@ -2346,14 +2346,14 @@ void idpf_wait_for_sw_marker_completion(const > struct idpf_tx_queue *txq) > target = complq->txq_grp->txqs[id]; > > idpf_queue_clear(SW_MARKER, target); > - if (target == txq) > - break; > > next: > if (unlikely(++ntc == complq->desc_count)) { > ntc = 0; > gen_flag = !gen_flag; > } > + if (target == txq) Are tou sure that incremented ntc value is ever written back to complq->next_to_clean? Yes, the value of "ntc" is written back to "complq->next_to_clean" at the end of the function (at line 2360): complq->next_to_clean = ntc; Thank you, I don’t see it from the patch. > + break; > } while (time_before(jiffies, timeout)); > > idpf_queue_assign(GEN_CHK, complq, gen_flag); > -- > 2.52.0.351.gbe84eed79e-goog
