Re: [PATCH] VirtioConsole support.

From: Konrad Rzeszutek Wilk
Date: Thu Oct 27 2011 - 17:56:28 EST

On Thu, Oct 27, 2011 at 02:43:22PM -0700, Miche Baker-Harvey wrote:
> Multiple HVC console terminals enabled.

Miche,

You might want to flesh out the description a bit. Perhaps include
such details as : "fixes the infinite loop that git commit XX
caused". Perhaps include some of the serial console output.

Maybe also change the title - the patch name (which is what shows up
if you do 'git log --oneline') is 'VirtioConsole support.' which is
not very informative.

Oh, and make sure to have the maintainers of the drivers/[tty|char]
in the 'To' field.

Cheers!
Konrad
>
> Serialize device and port open and initialization. Added a mutex
> which gates the handling of control messages in virtio_console.c.
> This includes adding and removing ports, and making opened ports be
> consoles. Extended the use of the prvdata spinlock to cover some missed
> modifications to prvdata.next_vtermno.
>
> I also added a mutex in hvc_console::hvc_alloc() to coordinate waiting
> for the driver to be ready, and for the one-time call to hvc_init(). It
> had been the case that this was sometimes being called mulitple times, and
> partially setup state was being used by the second caller of hvc_alloc().
>
> Make separate struct console* for each new port. There was a single static
> struct console* hvc_console, to be used for early printk. We aren't doing
> early printk, but more importantly, there is no code to multiplex on that
> one console. Multiple virtio_console ports were "sharing" this, which was
> disasterous since both the index and the flags for the console are stored
> there. The console struct is remembered in the hvc_struct, and it is
> deallocated when the hvc_struct is deallocated.
>
> Signed-off-by: Miche Baker-Harvey <miche@xxxxxxxxxx>
> Reported-by-and-Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
> drivers/char/virtio_console.c | 22 +++++++++++++++++++---
> drivers/tty/hvc/hvc_console.c | 39 +++++++++++++++++++++++++++++++++------
> drivers/tty/hvc/hvc_console.h | 1 +
> 3 files changed, 53 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index fb68b12..e819d46 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -24,6 +24,7 @@
> #include <linux/fs.h>
> #include <linux/init.h>
> #include <linux/list.h>
> +#include <linux/mutex.h>
> #include <linux/poll.h>
> #include <linux/sched.h>
> #include <linux/slab.h>
> @@ -95,6 +96,11 @@ struct console {
> u32 vtermno;
> };
>
> +/* serialize the handling of control messages, which includes
> + * the initialization of the virtio_consoles.
> + */
> +static DEFINE_MUTEX(virtio_console_mutex);
> +
> struct port_buffer {
> char *buf;
>
> @@ -979,8 +985,14 @@ int init_port_console(struct port *port)
> * pointers. The final argument is the output buffer size: we
> * can do any size, so we put PAGE_SIZE here.
> */
> - port->cons.vtermno = pdrvdata.next_vtermno;
> + spin_lock_irq(&pdrvdata_lock);
> + port->cons.vtermno = pdrvdata.next_vtermno++;
> + spin_unlock_irq(&pdrvdata_lock);
>
> + /*
> + * xxx Use index 0 for now assuming there is no early HVC, since
> + * we don't support it.
> + */
> port->cons.hvc = hvc_alloc(port->cons.vtermno, 0, &hv_ops, PAGE_SIZE);
> if (IS_ERR(port->cons.hvc)) {
> ret = PTR_ERR(port->cons.hvc);
> @@ -990,7 +1002,6 @@ int init_port_console(struct port *port)
> return ret;
> }
> spin_lock_irq(&pdrvdata_lock);
> - pdrvdata.next_vtermno++;
> list_add_tail(&port->cons.list, &pdrvdata.consoles);
> spin_unlock_irq(&pdrvdata_lock);
> port->guest_connected = true;
> @@ -1317,7 +1328,6 @@ static void handle_control_message(struct ports_device *portdev,
> int err;
>
> cpkt = (struct virtio_console_control *)(buf->buf + buf->offset);
> -
> port = find_port_by_id(portdev, cpkt->id);
> if (!port && cpkt->event != VIRTIO_CONSOLE_PORT_ADD) {
> /* No valid header at start of buffer. Drop it. */
> @@ -1326,6 +1336,11 @@ static void handle_control_message(struct ports_device *portdev,
> return;
> }
>
> + /*
> + * These are rare initialization-time events that should be
> + * serialized.
> + */
> + mutex_lock(&virtio_console_mutex);
> switch (cpkt->event) {
> case VIRTIO_CONSOLE_PORT_ADD:
> if (port) {
> @@ -1429,6 +1444,7 @@ static void handle_control_message(struct ports_device *portdev,
> }
> break;
> }
> + mutex_unlock(&virtio_console_mutex);
> }
>
> static void control_work_handler(struct work_struct *work)
> diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
> index 7430bc3..03ff6ed 100644
> --- a/drivers/tty/hvc/hvc_console.c
> +++ b/drivers/tty/hvc/hvc_console.c
> @@ -29,8 +29,9 @@
> #include <linux/kernel.h>
> #include <linux/kthread.h>
> #include <linux/list.h>
> -#include <linux/module.h>
> #include <linux/major.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> #include <linux/sysrq.h>
> #include <linux/tty.h>
> #include <linux/tty_flip.h>
> @@ -84,6 +85,10 @@ static LIST_HEAD(hvc_structs);
> * list traversal.
> */
> static DEFINE_SPINLOCK(hvc_structs_lock);
> +/*
> + * only one task does allocation at a time.
> + */
> +static DEFINE_MUTEX(hvc_ports_mutex);
>
> /*
> * This value is used to assign a tty->index value to a hvc_struct based
> @@ -242,6 +247,7 @@ static void destroy_hvc_struct(struct kref *kref)
>
> spin_unlock(&hvc_structs_lock);
>
> + kfree(hp->hvc_console);
> kfree(hp);
> }
>
> @@ -822,19 +828,25 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
> int outbuf_size)
> {
> struct hvc_struct *hp;
> + struct console *cp;
> int i;
>
> /* We wait until a driver actually comes along */
> + mutex_lock(&hvc_ports_mutex);
> if (!hvc_driver) {
> int err = hvc_init();
> - if (err)
> + if (err) {
> + mutex_unlock(&hvc_ports_mutex);
> return ERR_PTR(err);
> + }
> }
>
> hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
> GFP_KERNEL);
> - if (!hp)
> + if (!hp) {
> + mutex_unlock(&hvc_ports_mutex);
> return ERR_PTR(-ENOMEM);
> + }
>
> hp->vtermno = vtermno;
> hp->data = data;
> @@ -845,6 +857,19 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
> kref_init(&hp->kref);
>
> INIT_WORK(&hp->tty_resize, hvc_set_winsz);
> + /*
> + * make each console its own struct console.
> + * No need to do allocation and copy under lock.
> + */
> + cp = kzalloc(sizeof(*cp), GFP_KERNEL);
> + if (!cp) {
> + kfree(hp);
> + mutex_unlock(&hvc_ports_mutex);
> + return ERR_PTR(-ENOMEM);
> + }
> + memcpy(cp, &hvc_console, sizeof(*cp));
> + hp->hvc_console = cp;
> +
> spin_lock_init(&hp->lock);
> spin_lock(&hvc_structs_lock);
>
> @@ -862,13 +887,14 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
> i = ++last_hvc;
>
> hp->index = i;
> - hvc_console.index = i;
> + cp->index = i;
> vtermnos[i] = vtermno;
> cons_ops[i] = ops;
>
> list_add_tail(&(hp->next), &hvc_structs);
> spin_unlock(&hvc_structs_lock);
> - register_console(&hvc_console);
> + register_console(cp);
> + mutex_unlock(&hvc_ports_mutex);
>
> return hp;
> }
> @@ -879,7 +905,8 @@ int hvc_remove(struct hvc_struct *hp)
> unsigned long flags;
> struct tty_struct *tty;
>
> - unregister_console(&hvc_console);
> + BUG_ON(!hp->hvc_console);
> + unregister_console(hp->hvc_console);
> spin_lock_irqsave(&hp->lock, flags);
> tty = tty_kref_get(hp->tty);
>
> diff --git a/drivers/tty/hvc/hvc_console.h b/drivers/tty/hvc/hvc_console.h
> index c335a14..2d20ab7 100644
> --- a/drivers/tty/hvc/hvc_console.h
> +++ b/drivers/tty/hvc/hvc_console.h
> @@ -58,6 +58,7 @@ struct hvc_struct {
> const struct hv_ops *ops;
> int irq_requested;
> int data;
> + struct console *hvc_console;
> struct winsize ws;
> struct work_struct tty_resize;
> struct list_head next;
> --
> 1.7.3.1
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