s390/sclp: add parameter to specify number of buffer pages

Add a kernel parameter to be able to specify the number of pages to be
used as output buffer by the line-mode sclp driver and the vt220 sclp
driver. The current number of output pages is 6, if the service element
is unavailable the boot messages alone can fill up the output buffer.
If this happens the system blocks until the service element is working
again. For a large LPAR with many devices it is sensible to have the
ability to increase the output buffer size. To help to debug this
situation add a counter for the page-pool-empty situation and make it
available as a sclp driver attribute.
To avoid the system to stall until the service element works again
add another kernel parameter to allow to drop output buffers.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/drivers/s390/char/sclp.c b/drivers/s390/char/sclp.c
index bd6871bf545a67200a5e4af4c672fb18f0193f0c..a77febeead1fdd4fea04eb56969d377d6a18caca 100644 (file)
--- a/drivers/s390/char/sclp.c
+++ b/drivers/s390/char/sclp.c
@@ -50,11 +50,42 @@ static char sclp_init_sccb[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
 /* Suspend request */
 static DECLARE_COMPLETION(sclp_request_queue_flushed);
 
+/* Number of console pages to allocate, used by sclp_con.c and sclp_vt220.c */
+int sclp_console_pages = SCLP_CONSOLE_PAGES;
+/* Flag to indicate if buffer pages are dropped on buffer full condition */
+int sclp_console_drop = 0;
+/* Number of times the console dropped buffer pages */
+unsigned long sclp_console_full;
+
 static void sclp_suspend_req_cb(struct sclp_req *req, void *data)
 {
        complete(&sclp_request_queue_flushed);
 }
 
+static int __init sclp_setup_console_pages(char *str)
+{
+       int pages, rc;
+
+       rc = kstrtoint(str, 0, &pages);
+       if (!rc && pages >= SCLP_CONSOLE_PAGES)
+               sclp_console_pages = pages;
+       return 1;
+}
+
+__setup("sclp_con_pages=", sclp_setup_console_pages);
+
+static int __init sclp_setup_console_drop(char *str)
+{
+       int drop, rc;
+
+       rc = kstrtoint(str, 0, &drop);
+       if (!rc && drop)
+               sclp_console_drop = 1;
+       return 1;
+}
+
+__setup("sclp_con_drop=", sclp_setup_console_drop);
+
 static struct sclp_req sclp_suspend_req;
 
 /* Timer for request retries. */
@@ -1013,11 +1044,47 @@ static const struct dev_pm_ops sclp_pm_ops = {
        .restore        = sclp_restore,
 };
 
+static ssize_t sclp_show_console_pages(struct device_driver *dev, char *buf)
+{
+       return sprintf(buf, "%i\n", sclp_console_pages);
+}
+
+static DRIVER_ATTR(con_pages, S_IRUSR, sclp_show_console_pages, NULL);
+
+static ssize_t sclp_show_con_drop(struct device_driver *dev, char *buf)
+{
+       return sprintf(buf, "%i\n", sclp_console_drop);
+}
+
+static DRIVER_ATTR(con_drop, S_IRUSR, sclp_show_con_drop, NULL);
+
+static ssize_t sclp_show_console_full(struct device_driver *dev, char *buf)
+{
+       return sprintf(buf, "%lu\n", sclp_console_full);
+}
+
+static DRIVER_ATTR(con_full, S_IRUSR, sclp_show_console_full, NULL);
+
+static struct attribute *sclp_drv_attrs[] = {
+       &driver_attr_con_pages.attr,
+       &driver_attr_con_drop.attr,
+       &driver_attr_con_full.attr,
+       NULL,
+};
+static struct attribute_group sclp_drv_attr_group = {
+       .attrs = sclp_drv_attrs,
+};
+static const struct attribute_group *sclp_drv_attr_groups[] = {
+       &sclp_drv_attr_group,
+       NULL,
+};
+
 static struct platform_driver sclp_pdrv = {
        .driver = {
                .name   = "sclp",
                .owner  = THIS_MODULE,
                .pm     = &sclp_pm_ops,
+               .groups = sclp_drv_attr_groups,
        },
 };
 
@@ -1096,10 +1163,12 @@ static __init int sclp_initcall(void)
        rc = platform_driver_register(&sclp_pdrv);
        if (rc)
                return rc;
+
        sclp_pdev = platform_device_register_simple("sclp", -1, NULL, 0);
        rc = IS_ERR(sclp_pdev) ? PTR_ERR(sclp_pdev) : 0;
        if (rc)
                goto fail_platform_driver_unregister;
+
        rc = atomic_notifier_chain_register(&panic_notifier_list,
                                            &sclp_on_panic_nb);
        if (rc)

diff --git a/drivers/s390/char/sclp.h b/drivers/s390/char/sclp.h
index 25bcd4c0ed82d35f522f4d0efdd7477ec6076a01..e11383f5d3d2c2e3bb093397b39adec2191d872c 100644 (file)
--- a/drivers/s390/char/sclp.h
+++ b/drivers/s390/char/sclp.h
@@ -15,7 +15,7 @@
 
 /* maximum number of pages concerning our own memory management */
 #define MAX_KMEM_PAGES (sizeof(unsigned long) << 3)
-#define MAX_CONSOLE_PAGES      6
+#define SCLP_CONSOLE_PAGES     6
 
 #define EVTYP_OPCMD            0x01
 #define EVTYP_MSG              0x02
@@ -175,6 +175,10 @@ int sclp_service_call(sclp_cmdw_t command, void *sccb);
 int sclp_sdias_init(void);
 void sclp_sdias_exit(void);
 
+extern int sclp_console_pages;
+extern int sclp_console_drop;
+extern unsigned long sclp_console_full;
+
 /* useful inlines */
 
 /* VM uses EBCDIC 037, LPAR+native(SE+HMC) use EBCDIC 500 */

diff --git a/drivers/s390/char/sclp_con.c b/drivers/s390/char/sclp_con.c
index ecf45c54f8c469c84da45049e006225593283a90..5880def98fc1be4dbfedbfa166d725a52ffc35c2 100644 (file)
--- a/drivers/s390/char/sclp_con.c
+++ b/drivers/s390/char/sclp_con.c
@@ -129,6 +129,31 @@ sclp_console_timeout(unsigned long data)
        sclp_conbuf_emit();
 }
 
+/*
+ * Drop oldest console buffer if sclp_con_drop is set
+ */
+static int
+sclp_console_drop_buffer(void)
+{
+       struct list_head *list;
+       struct sclp_buffer *buffer;
+       void *page;
+
+       if (!sclp_console_drop)
+               return 0;
+       list = sclp_con_outqueue.next;
+       if (sclp_con_queue_running)
+               /* The first element is in I/O */
+               list = list->next;
+       if (list == &sclp_con_outqueue)
+               return 0;
+       list_del(list);
+       buffer = list_entry(list, struct sclp_buffer, list);
+       page = sclp_unmake_buffer(buffer);
+       list_add_tail((struct list_head *) page, &sclp_con_pages);
+       return 1;
+}
+
 /*
  * Writes the given message to S390 system console
  */
@@ -150,9 +175,13 @@ sclp_console_write(struct console *console, const char *message,
        do {
                /* make sure we have a console output buffer */
                if (sclp_conbuf == NULL) {
+                       if (list_empty(&sclp_con_pages))
+                               sclp_console_full++;
                        while (list_empty(&sclp_con_pages)) {
                                if (sclp_con_suspended)
                                        goto out;
+                               if (sclp_console_drop_buffer())
+                                       break;
                                spin_unlock_irqrestore(&sclp_con_lock, flags);
                                sclp_sync_wait();
                                spin_lock_irqsave(&sclp_con_lock, flags);
@@ -297,7 +326,7 @@ sclp_console_init(void)
                return rc;
        /* Allocate pages for output buffering */
        INIT_LIST_HEAD(&sclp_con_pages);
-       for (i = 0; i < MAX_CONSOLE_PAGES; i++) {
+       for (i = 0; i < sclp_console_pages; i++) {
                page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
                list_add_tail(page, &sclp_con_pages);
        }

diff --git a/drivers/s390/char/sclp_vt220.c b/drivers/s390/char/sclp_vt220.c
index 5aaaa2ec8df44f4547c70b9f80d5c628c6d9d591..4eed38cd0af629b87108289174a81a9c5dedb44c 100644 (file)
--- a/drivers/s390/char/sclp_vt220.c
+++ b/drivers/s390/char/sclp_vt220.c
@@ -362,6 +362,31 @@ sclp_vt220_timeout(unsigned long data)
 
 #define BUFFER_MAX_DELAY       HZ/20
 
+/*
+ * Drop oldest console buffer if sclp_con_drop is set
+ */
+static int
+sclp_vt220_drop_buffer(void)
+{
+       struct list_head *list;
+       struct sclp_vt220_request *request;
+       void *page;
+
+       if (!sclp_console_drop)
+               return 0;
+       list = sclp_vt220_outqueue.next;
+       if (sclp_vt220_queue_running)
+               /* The first element is in I/O */
+               list = list->next;
+       if (list == &sclp_vt220_outqueue)
+               return 0;
+       list_del(list);
+       request = list_entry(list, struct sclp_vt220_request, list);
+       page = request->sclp_req.sccb;
+       list_add_tail((struct list_head *) page, &sclp_vt220_empty);
+       return 1;
+}
+
 /* 
  * Internal implementation of the write function. Write COUNT bytes of data
  * from memory at BUF
@@ -390,12 +415,16 @@ __sclp_vt220_write(const unsigned char *buf, int count, int do_schedule,
        do {
                /* Create an sclp output buffer if none exists yet */
                if (sclp_vt220_current_request == NULL) {
+                       if (list_empty(&sclp_vt220_empty))
+                               sclp_console_full++;
                        while (list_empty(&sclp_vt220_empty)) {
-                               spin_unlock_irqrestore(&sclp_vt220_lock, flags);
                                if (may_fail || sclp_vt220_suspended)
                                        goto out;
-                               else
-                                       sclp_sync_wait();
+                               if (sclp_vt220_drop_buffer())
+                                       break;
+                               spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+
+                               sclp_sync_wait();
                                spin_lock_irqsave(&sclp_vt220_lock, flags);
                        }
                        page = (void *) sclp_vt220_empty.next;
@@ -428,8 +457,8 @@ __sclp_vt220_write(const unsigned char *buf, int count, int do_schedule,
                sclp_vt220_timer.expires = jiffies + BUFFER_MAX_DELAY;
                add_timer(&sclp_vt220_timer);
        }
-       spin_unlock_irqrestore(&sclp_vt220_lock, flags);
 out:
+       spin_unlock_irqrestore(&sclp_vt220_lock, flags);
        return overall_written;
 }
 
@@ -803,7 +832,7 @@ sclp_vt220_con_init(void)
 
        if (!CONSOLE_IS_SCLP)
                return 0;
-       rc = __sclp_vt220_init(MAX_CONSOLE_PAGES);
+       rc = __sclp_vt220_init(sclp_console_pages);
        if (rc)
                return rc;
        /* Attach linux console */