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| author | John Ogness <john.ogness@linutronix.de> | 2020-07-07 17:22:04 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2020-07-16 20:40:39 +0200 |
| commit | 632ca50f2cbd8809a2fc1934b4b2c9c49bd55e98 (patch) | |
| tree | 17ed0b6ce864b175f2849f7518b7648853618f3c /net | |
| parent | Merge branch 'net-fec-a-few-improvements' (diff) | |
| download | linux-632ca50f2cbd8809a2fc1934b4b2c9c49bd55e98.tar.xz linux-632ca50f2cbd8809a2fc1934b4b2c9c49bd55e98.zip | |
af_packet: TPACKET_V3: replace busy-wait loop
A busy-wait loop is used to implement waiting for bits to be copied
from the skb to the kernel buffer before retiring a block. This is
a problem on PREEMPT_RT because the copying task could be preempted
by the busy-waiting task and thus live lock in the busy-wait loop.
Replace the busy-wait logic with an rwlock_t. This provides lockdep
coverage and makes the code RT ready.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/packet/af_packet.c | 20 | ||||
| -rw-r--r-- | net/packet/internal.h | 2 |
2 files changed, 11 insertions, 11 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 7b436ebde61d..781fee93b7d5 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -593,6 +593,7 @@ static void init_prb_bdqc(struct packet_sock *po, req_u->req3.tp_block_size); p1->tov_in_jiffies = msecs_to_jiffies(p1->retire_blk_tov); p1->blk_sizeof_priv = req_u->req3.tp_sizeof_priv; + rwlock_init(&p1->blk_fill_in_prog_lock); p1->max_frame_len = p1->kblk_size - BLK_PLUS_PRIV(p1->blk_sizeof_priv); prb_init_ft_ops(p1, req_u); @@ -659,10 +660,9 @@ static void prb_retire_rx_blk_timer_expired(struct timer_list *t) * */ if (BLOCK_NUM_PKTS(pbd)) { - while (atomic_read(&pkc->blk_fill_in_prog)) { - /* Waiting for skb_copy_bits to finish... */ - cpu_relax(); - } + /* Waiting for skb_copy_bits to finish... */ + write_lock(&pkc->blk_fill_in_prog_lock); + write_unlock(&pkc->blk_fill_in_prog_lock); } if (pkc->last_kactive_blk_num == pkc->kactive_blk_num) { @@ -921,10 +921,9 @@ static void prb_retire_current_block(struct tpacket_kbdq_core *pkc, * the timer-handler already handled this case. */ if (!(status & TP_STATUS_BLK_TMO)) { - while (atomic_read(&pkc->blk_fill_in_prog)) { - /* Waiting for skb_copy_bits to finish... */ - cpu_relax(); - } + /* Waiting for skb_copy_bits to finish... */ + write_lock(&pkc->blk_fill_in_prog_lock); + write_unlock(&pkc->blk_fill_in_prog_lock); } prb_close_block(pkc, pbd, po, status); return; @@ -944,7 +943,8 @@ static int prb_queue_frozen(struct tpacket_kbdq_core *pkc) static void prb_clear_blk_fill_status(struct packet_ring_buffer *rb) { struct tpacket_kbdq_core *pkc = GET_PBDQC_FROM_RB(rb); - atomic_dec(&pkc->blk_fill_in_prog); + + read_unlock(&pkc->blk_fill_in_prog_lock); } static void prb_fill_rxhash(struct tpacket_kbdq_core *pkc, @@ -998,7 +998,7 @@ static void prb_fill_curr_block(char *curr, pkc->nxt_offset += TOTAL_PKT_LEN_INCL_ALIGN(len); BLOCK_LEN(pbd) += TOTAL_PKT_LEN_INCL_ALIGN(len); BLOCK_NUM_PKTS(pbd) += 1; - atomic_inc(&pkc->blk_fill_in_prog); + read_lock(&pkc->blk_fill_in_prog_lock); prb_run_all_ft_ops(pkc, ppd); } diff --git a/net/packet/internal.h b/net/packet/internal.h index 907f4cd2a718..fd41ecb7f605 100644 --- a/net/packet/internal.h +++ b/net/packet/internal.h @@ -39,7 +39,7 @@ struct tpacket_kbdq_core { char *nxt_offset; struct sk_buff *skb; - atomic_t blk_fill_in_prog; + rwlock_t blk_fill_in_prog_lock; /* Default is set to 8ms */ #define DEFAULT_PRB_RETIRE_TOV (8) |