From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83B6D3C5DD4; Mon, 7 Sep 2026 09:53:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788774828; cv=none; b=ZVRLglpaaJ63iLp4guZloNxvxW9uRw2wp0orsTcafim3amu7B8SMU2KOx+YLfbXSiyAJ54TveWWTmM3QAsy7h5Ihy3z8JKyudJeAOuV4llDkDEOA5OANCbTXKeyGgmpudBIAWpxz+xU6flQrxWEw7Ag/hTxgevDKAg8DZTwcEtE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788774828; c=relaxed/simple; bh=UxNHWxv1lAarQTLq2idNJ5bq3LxFHRqO1kuxGq1Hocs=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=NDh7bB9BavU5C0WMesgVrzDHEkxHi0gat8LaZabAEw9OkucDHdfg5tG4Er/TZhxF0TuQEric2tMSydMVDfjQIW61TWC/wPjXjAbc/xBo7Iq5Xz4OKtU4rqkuzTnfmgCnVJDNsr4ZTtHBr5lp5xyeSkZ47FCy7By7KmhaR/cDL9Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z56s0K8Z; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z56s0K8Z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DBCAB1F00A3A; Mon, 7 Sep 2026 09:53:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788774826; bh=q/COAdYlU0pd0l5RbIN0tn1G/83IKZjnvQXUajavTxg=; h=From:To:Cc:Subject:Date; b=Z56s0K8ZoMBUmqgpQEmLfzcwD26KsOTmwWjY45aBofAofQxKmNszGVWBfOH4vn2Mc H6tGIDCy43fIGxbWYEnz8Gg4g1uNr0YA8DcbU+95/jmsLnY4OW/2zYOypDG9KS6GqL GajdYL8TYmP+KF3U4R7i6+qLT7Cf5kFpqPWSfo9KwfKov80gkR+MDS/gB2kt4QZJM3 ikeZTWaQKmPdliryOyeOJvHPIaDw5YzTe8/lhRWiCbCm9mJUSN6QO14NT3AA3J/LRr ASNHBL6W1T6dIOgj4gsR4DmLukRlXV+ftLCq/oo4H/yvMejG3SwLXJA0ugDPlMwMjW pev+xpoSeYkJQ== Received: from johan by xi.lan with local (Exim 4.99.4) (envelope-from ) id 1x3W2q-00000000Y1s-2sh6; Mon, 07 Sep 2026 11:53:44 +0200 From: Johan Hovold To: David Lin , Johan Hovold , Alex Elder , Greg Kroah-Hartman Cc: greybus-dev@lists.linaro.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v2] staging: greybus: uart: fix racy TIOCMIWAIT implementation Date: Mon, 7 Sep 2026 11:53:05 +0200 Message-ID: <20260907095305.130762-1-johan@kernel.org> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Check the wakeup condition after adding the task to the waitqueue and updating the task state to avoid missing a racing modem status update or disconnect. Store the old icount on entry and do not update it in the completion handler to avoid missing events or reporting spurious ones (due to modem status changes before TIOCMIWAIT was called). Fixes: e68453ed28c5 ("greybus: uart-gb: now builds, more framework added") Cc: stable@vger.kernel.org # 4.9 Cc: Greg Kroah-Hartman Signed-off-by: Johan Hovold --- Changes in v2 - store old icount on entry only drivers/staging/greybus/uart.c | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c index 24b4dab069c3..d47f00751e7a 100644 --- a/drivers/staging/greybus/uart.c +++ b/drivers/staging/greybus/uart.c @@ -53,7 +53,6 @@ struct gb_tty { spinlock_t read_lock; spinlock_t write_lock; struct async_icount iocount; - struct async_icount oldcount; wait_queue_head_t wioctl; struct mutex mutex; u8 ctrlin; /* input control lines */ @@ -643,11 +642,16 @@ static int wait_serial_change(struct gb_tty *gb_tty, unsigned long arg) if (!(arg & (TIOCM_DSR | TIOCM_RI | TIOCM_CD))) return -EINVAL; - do { + spin_lock_irq(&gb_tty->read_lock); + old = gb_tty->iocount; + spin_unlock_irq(&gb_tty->read_lock); + + add_wait_queue(&gb_tty->wioctl, &wait); + for (;;) { + set_current_state(TASK_INTERRUPTIBLE); + spin_lock_irq(&gb_tty->read_lock); - old = gb_tty->oldcount; new = gb_tty->iocount; - gb_tty->oldcount = new; spin_unlock_irq(&gb_tty->read_lock); if ((arg & TIOCM_DSR) && (old.dsr != new.dsr)) @@ -657,18 +661,20 @@ static int wait_serial_change(struct gb_tty *gb_tty, unsigned long arg) if ((arg & TIOCM_RI) && (old.rng != new.rng)) break; - add_wait_queue(&gb_tty->wioctl, &wait); - set_current_state(TASK_INTERRUPTIBLE); - schedule(); - remove_wait_queue(&gb_tty->wioctl, &wait); if (gb_tty->disconnected) { - if (arg & TIOCM_CD) - break; retval = -ENODEV; - } else if (signal_pending(current)) { + break; + } + + schedule(); + + if (signal_pending(current)) { retval = -ERESTARTSYS; + break; } - } while (!retval); + } + __set_current_state(TASK_RUNNING); + remove_wait_queue(&gb_tty->wioctl, &wait); return retval; } -- 2.55.0