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Fri, 23 Oct 2026 13:40:40 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id PK1eK9hj22ohVgAAD6G6ig (envelope-from ); Fri, 23 Oct 2026 13:40:40 +0000 Date: Fri, 23 Oct 2026 15:40:40 +0200 Message-ID: <87cxt0a61z.wl-tiwai@suse.de> From: Takashi Iwai To: Cen Zhang Cc: perex@perex.cz, tiwai@suse.com, linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, tiwai@suse.de, baijiaju1990@gmail.com, jjzuming@gmail.com Subject: Re: [PATCH v3] ALSA: pcm: Drain proc callbacks at device disconnect In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/30.2 Mule/6.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Spamd-Result: default: False [-12.51 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FREEMAIL_TO(0.00)[gmail.com]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[perex.cz,suse.com,vger.kernel.org,suse.de,gmail.com]; RCPT_COUNT_SEVEN(0.00)[8]; RCVD_VIA_SMTP_AUTH(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.de:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:email,suse.de:dkim] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -12.51 X-Spam-Level: X-Rspamd-Queue-Id: 3399B220E2 On Thu, 22 Oct 2026 12:58:20 +0200, Cen Zhang wrote: > > Disconnecting an individual PCM leaves its proc files accessible until > snd_pcm_free_stream(). HDA codec-only sysfs unbind can take this path > while the controller and card remain registered. An open proc file pins > the card module, but does not hold a codec PCM reference. > > With CONFIG_SND_VERBOSE_PROCFS, a prealloc write is buffered until file > release. Without an attached PCM runtime, its release can replace the > DMA buffer after final PCM cleanup has already freed the preallocation: > > HDA codec unbind prealloc file release > ---------------- --------------------- > hda_codec_driver_remove() > snd_hda_codec_disconnect_pcms() > snd_device_disconnect() > snd_pcm_dev_disconnect() > /* proc nodes remain */ > snd_hda_codec_cleanup_for_unbind() > codec_release_pcms() > snd_device_free() > snd_pcm_free() > free preallocated buffer > snd_info_text_entry_release() > snd_pcm_lib_preallocate_proc_write() > replace DMA buffer > remove stream proc nodes > free substream > > The later proc rundown can itself invoke this buffered write and leave > the replacement allocation without a final free. A concurrent release > can also overlap the earlier buffer cleanup. > > Extract snd_info_disconnect_entry() from snd_info_free_entry() to remove > proc nodes and drain callbacks without freeing the info entry objects. > Use it for both stream directions at PCM disconnect. Finish the existing > PCM state and device disconnection under open_mutex, then drop that lock > before proc rundown: even an otherwise idle proc file can run its > buffered release callback, which takes open_mutex, during proc_remove(). > > Keep entry ownership and final cleanup unchanged, including the saved > OSS child entries. As with existing info entry teardown, callers must > serialize registration with disconnection and release. > > Suggested-by: Takashi Iwai > Assisted-by: LLM > Signed-off-by: Cen Zhang Applied now. Although we still may have some issues about the concurrent codec release and probe, this should be treated better in the upper layer. thanks, Takashi