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Wed, 4 Nov 2026 19:30:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793820629; bh=8PrbyLDFAjoLX2WIUniAe1t4rzdjlrNCOM5s/iYEHW4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gJgUQqFPUdfHqbzO0yydZhimAxOsTiy3j7Gg5403vTetiLd8TkhBazxxcEfGmzx5W rVciL31qjq1dJ+7plUgL+tdmo2E2SJQ7PTYtqCx2yA5ZQXmFwpTZ/BfdBiLoaoCUxG lL06dxOJ7GUHhT6w/GTxKhllfZZxjGQKGJLvM2FgsjQySeffSyuwGPa5N1ogUjy23k pyZhFAReGbPqZK/rsbfRogg889zRCaP4JZXtWySOnvmSw9BhOsw3KUl59GOvqooX4d kXIZOW4f1sN3bBLyMvSBrt7Ky8oqzKQD4BdDN9Z0S+Gea/SE9ghcz9qcFKMYoNacQt L85SUfBFwN3lg== From: Christian Brauner To: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Jann Horn , Josef Bacik , Chris Mason , Jeff Layton , NeilBrown , Eric Dumazet , Thomas Gleixner , Al Viro , Jonathan Corbet , Christoph Hellwig , Greg Kroah-Hartman , Joel Granados , Kees Cook , Jan Kara , Jan Kara , linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-um@lists.infradead.org, linux-wireless@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, ntfs3@lists.linux.dev, platform-driver-x86@vger.kernel.org, coreteam@netfilter.org, kexec@lists.infradead.org, linux-pci@vger.kernel.org, linux-sound@vger.kernel.org, netfilter-devel@vger.kernel.org, dri-devel@lists.freedesktop.org, ibm-acpi-devel@lists.sourceforge.net, jfs-discussion@lists.sourceforge.net, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-cifs@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-mm@kvack.org, linux-sh@vger.kernel.org, linux-usb@vger.kernel.org, samba-technical@lists.samba.org, sparclinux@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-doc@vger.kernel.org, linux-serial@vger.kernel.org, linux-atm-general@lists.sourceforge.net, Takashi Iwai , linux-input@vger.kernel.org, linux-raid@vger.kernel.org, linux-ext4@vger.kernel.org, linux-modules@vger.kernel.org, linux-debuggers@vger.kernel.org, "Christian Brauner (Amutable)" , Chuck Lever Subject: [PATCH RESEND v2 04/23] proc: wait for the last user of an entry with wait_var_event() Date: Wed, 4 Nov 2026 20:30:15 +0100 Message-ID: <20261104-work-procfs-core-v2-4-76ace653a773@kernel.org> In-Reply-To: <20261104-work-procfs-core-v2-0-76ace653a773@kernel.org> References: <20261104-work-procfs-core-v2-0-76ace653a773@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2591; i=brauner@kernel.org; h=from:subject:message-id; bh=fMKtT8cQ8gIJJgjvKUq4bmwIClHWmBxP0YQIj81mIGk=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9bi+tjeLVK3NRu/3AwmDiBg69+Yv9Pl1qUCpOO/S4p eB88dITHaUsDGJcDLJiiiwO7Sbhcst5KjYbZWrAzGFlAhnCwMUpABPp+s7wP+3hike1RRfnnrx8 7ZbO37kO/mV/VGsDH0zbcnLeweWXS50Z/ucLe5/PfHaXt52J1YN/QouDsniPCP+rzsMti01ecAp LcAIA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit X-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-um" X-Spam-Status: No, score=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 proc_entry_rundown() waits for the last user of an entry with a completion on its stack that it points the entry at while it waits. That's a pointer in every struct proc_dir_entry for something that happens once in the life of an entry, if at all. Wait on the count itself with wait_var_event() instead and let unuse_pde() wake the waiter with wake_up_var() when the count hits the bias. The waiters sleep on the hashed wait queues behind that, so procfs doesn't need a wait queue of its own for this, neither in the entry nor a global one. kernfs keeps one per root for the same thing, deactivate_waitq. Note that atomic_dec_return() is fully ordered, so the count is visible before wake_up_var() looks for waiters. No functional changes. Signed-off-by: Christian Brauner (Amutable) --- fs/proc/inode.c | 7 +++---- fs/proc/internal.h | 1 - 2 files changed, 3 insertions(+), 5 deletions(-) diff --git a/fs/proc/inode.c b/fs/proc/inode.c index 66a3688757dd..8795add1898d 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -25,6 +25,7 @@ #include #include #include +#include #include "internal.h" @@ -203,7 +204,7 @@ static inline int use_pde(struct proc_dir_entry *pde) static void unuse_pde(struct proc_dir_entry *pde) { if (unlikely(atomic_dec_return(&pde->in_use) == BIAS)) - complete(pde->pde_unload_completion); + wake_up_var(&pde->in_use); } /* Pin an entry that can go away around a call into it, see use_pde(). */ @@ -266,11 +267,9 @@ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo) void proc_entry_rundown(struct proc_dir_entry *de) { - DECLARE_COMPLETION_ONSTACK(c); /* Wait until all existing callers into module are done. */ - de->pde_unload_completion = &c; if (atomic_add_return(BIAS, &de->in_use) != BIAS) - wait_for_completion(&c); + wait_var_event(&de->in_use, atomic_read(&de->in_use) == BIAS); /* ->pde_openers list can't grow from now on. */ diff --git a/fs/proc/internal.h b/fs/proc/internal.h index 6b61d09ac5e5..ab4d7bd1fb75 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -38,7 +38,6 @@ struct proc_dir_entry { struct list_head pde_openers; /* who did ->open, but not ->release */ /* protects ->pde_openers and all struct pde_opener instances */ spinlock_t pde_unload_lock; - struct completion *pde_unload_completion; const struct inode_operations *proc_iops; union { const struct proc_ops *proc_ops; -- 2.53.0