linux-kernel - [PATCH v3 3/3] ALSA: firewire-lib: amdtp-stream work queue inline description

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240729214149.752663-4-edmund.raile@protonmail.com>
Date: Mon, 29 Jul 2024 21:42:26 +0000
From: Edmund Raile <edmund.raile@...tonmail.com>
To: o-takashi@...amocchi.jp, clemens@...isch.de
Cc: tiwai@...e.com, alsa-devel@...a-project.org, linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH v3 3/3] ALSA: firewire-lib: amdtp-stream work queue inline description

Replace prior inline description to prevent future deadlock.

Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/kwryofzdmjvzkuw6j3clftsxmoolynljztxqwg76hzeo4simnl@jn3eo7pe642q/
Signed-off-by: Edmund Raile <edmund.raile@...tonmail.com>
---
 sound/firewire/amdtp-stream.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index a07b0452267d..7438999e0510 100644
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -1857,20 +1857,12 @@ unsigned long amdtp_domain_stream_pcm_pointer(struct amdtp_domain *d,
 	struct amdtp_stream *irq_target = d->irq_target;
 
 	if (irq_target && amdtp_stream_running(irq_target)) {
-		// This function is called in software IRQ context of
-		// period_work or process context.
-		//
-		// When the software IRQ context was scheduled by software IRQ
-		// context of IT contexts, queued packets were already handled.
-		// Therefore, no need to flush the queue in buffer furthermore.
-		//
-		// When the process context reach here, some packets will be
-		// already queued in the buffer. These packets should be handled
-		// immediately to keep better granularity of PCM pointer.
-		//
-		// Later, the process context will sometimes schedules software
-		// IRQ context of the period_work. Then, no need to flush the
-		// queue by the same reason as described in the above
+		// use wq to prevent AB/BA deadlock competition for
+		// substream lock:
+		// fw_iso_context_flush_completions() acquires
+		// lock by ohci_flush_iso_completions(),
+		// amdtp-stream process_rx_packets() attempts to
+		// acquire same lock by snd_pcm_elapsed()
 		if (current_work() != &s->period_work)
 			fw_iso_context_flush_completions(irq_target->context);
 	}
-- 
2.45.2