linux-kernel - [PATCH 2/3] wifi: ath11k: mark ath11k_dp_rx_mon_mpdu

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Message-ID: <20241119-ath11k-noinline-v1-2-4ec0a8aa30b2@quicinc.com>
Date: Tue, 19 Nov 2024 07:47:39 -0800
From: Jeff Johnson <quic_jjohnson@...cinc.com>
To: Kalle Valo <kvalo@...nel.org>, Jeff Johnson <jjohnson@...nel.org>,
        "Nathan
 Chancellor" <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Bill Wendling <morbo@...gle.com>,
        Justin Stitt <justinstitt@...gle.com>,
        "Arnd Bergmann" <arnd@...nel.org>
CC: <linux-wireless@...r.kernel.org>, <ath11k@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <llvm@...ts.linux.dev>,
        Jeff Johnson
	<quic_jjohnson@...cinc.com>
Subject: [PATCH 2/3] wifi: ath11k: mark ath11k_dp_rx_mon_mpdu_pop() as
 noinline

When compiling the ath11k driver using clang with KASAN enabled, the
following warning is observed:

drivers/net/wireless/ath/ath11k/dp_rx.c:5244:5: warning: stack frame size (1304) exceeds limit (1024) in 'ath11k_dp_rx_process_mon_status' [-Wframe-larger-than]

This is similar to the issue found in ath12k/qmi.c that was discussed
in [1] and fixed with [2]. The issue is that clang inlining can
explode stack usage.

ath11k_dp_rx_process_mon_status() itself is a pretty
lightweight function, but it dispatches to several other functions
which do the real work:

ath11k_dp_rx_process_mon_status()
	ath11k_dp_rx_reap_mon_status_ring()
	ath11k_dp_rx_mon_dest_process()
		ath11k_dp_rx_mon_mpdu_pop() *
		ath11k_dp_rx_mon_deliver()
			ath11k_dp_rx_mon_merg_msdus()
			ath11k_dp_rx_deliver_msdu()
	ath11k_dp_rx_update_peer_stats()

Of these, only ath11k_dp_rx_mon_mpdu_pop() has non-trivial stack
usage, so mark that function as 'noinline_for_stack' to prevent it
from being inlined in ath11k_dp_rx_process_mon_status(), thereby
eliminating the excessive stack usage.

Link: https://msgid.link/bc214795-1c51-4cb7-922f-67d6ef98bff2@quicinc.com # [1]
Link: https://patch.msgid.link/20241028-ath12k_qmi_driver_event_work-v1-1-0d532eb593fa@quicinc.com # [2]
Signed-off-by: Jeff Johnson <quic_jjohnson@...cinc.com>
---
 drivers/net/wireless/ath/ath11k/dp_rx.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/dp_rx.c b/drivers/net/wireless/ath/ath11k/dp_rx.c
index 40088e62572e..f253fac116bc 100644
--- a/drivers/net/wireless/ath/ath11k/dp_rx.c
+++ b/drivers/net/wireless/ath/ath11k/dp_rx.c
@@ -4690,11 +4690,12 @@ static void ath11k_dp_mon_get_buf_len(struct hal_rx_msdu_desc_info *info,
 	}
 }
 
-static u32
-ath11k_dp_rx_mon_mpdu_pop(struct ath11k *ar, int mac_id,
-			  void *ring_entry, struct sk_buff **head_msdu,
-			  struct sk_buff **tail_msdu, u32 *npackets,
-			  u32 *ppdu_id)
+/* clang stack usage explodes if this is inlined */
+static noinline_for_stack
+u32 ath11k_dp_rx_mon_mpdu_pop(struct ath11k *ar, int mac_id,
+			      void *ring_entry, struct sk_buff **head_msdu,
+			      struct sk_buff **tail_msdu, u32 *npackets,
+			      u32 *ppdu_id)
 {
 	struct ath11k_pdev_dp *dp = &ar->dp;
 	struct ath11k_mon_data *pmon = (struct ath11k_mon_data *)&dp->mon_data;

-- 
2.42.0