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Message-Id: <1275938692-26997-1-git-send-email-fleitner@redhat.com>
Date: Mon, 7 Jun 2010 16:24:52 -0300
From: Flavio Leitner <fleitner@...hat.com>
To: netdev@...r.kernel.org
Cc: David Miller <davem@...emloft.net>, Cong Wang <amwang@...hat.com>,
Jay Vosburgh <fubar@...ibm.com>,
Flavio Leitner <fbl@...close.org>,
Matt Mackall <mpm@...enic.com>,
Andy Gospodarek <gospo@...hat.com>,
Neil Horman <nhorman@...driver.com>,
Jeff Moyer <jmoyer@...hat.com>,
Stephen Hemminger <shemminger@...ux-foundation.org>,
lkml <linux-kernel@...r.kernel.org>,
<bridge@...ts.linux-foundation.org>,
<bonding-devel@...ts.sourceforge.net>,
Flavio Leitner <fleitner@...hat.com>
Subject: [PATCH] netconsole: queue console messages to send later
There are some networking drivers that hold a lock in the
transmit path. Therefore, if a console message is printed
after that, netconsole will push it through the transmit path,
resulting in a deadlock.
This patch fixes the re-injection problem by queuing the console
messages in a preallocated circular buffer and then scheduling a
workqueue to send them later with another context.
Signed-off-by: Flavio Leitner <fleitner@...hat.com>
---
drivers/net/netconsole.c | 156 +++++++++++++++++++++++++++++++++++++++-------
1 files changed, 133 insertions(+), 23 deletions(-)
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index ca142c4..874376d 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -44,6 +44,8 @@
#include <linux/netpoll.h>
#include <linux/inet.h>
#include <linux/configfs.h>
+#include <linux/workqueue.h>
+#include <linux/circ_buf.h>
MODULE_AUTHOR("Maintainer: Matt Mackall <mpm@...enic.com>");
MODULE_DESCRIPTION("Console driver for network interfaces");
@@ -56,6 +58,10 @@ static char config[MAX_PARAM_LENGTH];
module_param_string(netconsole, config, MAX_PARAM_LENGTH, 0);
MODULE_PARM_DESC(netconsole, " netconsole=[src-port]@[src-ip]/[dev],[tgt-port]@<tgt-ip>/[tgt-macaddr]");
+static int logsize = PAGE_SIZE;
+module_param(logsize, int, 0444);
+MODULE_PARM_DESC(logsize, "netconsole buffer size");
+
#ifndef MODULE
static int __init option_setup(char *opt)
{
@@ -100,6 +106,75 @@ struct netconsole_target {
struct netpoll np;
};
+struct netconsole_msg_ctl {
+ struct circ_buf messages;
+ unsigned long ring_size;
+ struct page *buffer_page;
+ struct work_struct tx_work;
+};
+static struct netconsole_msg_ctl *netconsole_ctl;
+
+#define RING_INC_POS(pos, inc, size) ((pos + inc) & (size - 1))
+
+static void netconsole_target_get(struct netconsole_target *nt);
+static void netconsole_target_put(struct netconsole_target *nt);
+
+static void netconsole_start_xmit(const char *msg, unsigned int length)
+{
+ int frag, left;
+ unsigned long flags;
+ struct netconsole_target *nt;
+ const char *tmp;
+
+ /* Avoid taking lock and disabling interrupts unnecessarily */
+ if (list_empty(&target_list))
+ return;
+
+ spin_lock_irqsave(&target_list_lock, flags);
+ list_for_each_entry(nt, &target_list, list) {
+ netconsole_target_get(nt);
+ if (nt->enabled && netif_running(nt->np.dev)) {
+ /*
+ * We nest this inside the for-each-target loop above
+ * so that we're able to get as much logging out to
+ * at least one target if we die inside here, instead
+ * of unnecessarily keeping all targets in lock-step.
+ */
+ tmp = msg;
+ for (left = length; left;) {
+ frag = min(left, MAX_PRINT_CHUNK);
+ netpoll_send_udp(&nt->np, tmp, frag);
+ tmp += frag;
+ left -= frag;
+ }
+ }
+ netconsole_target_put(nt);
+ }
+ spin_unlock_irqrestore(&target_list_lock, flags);
+}
+
+static void netconsole_process_queue(struct work_struct *work)
+{
+ struct circ_buf *messages = &netconsole_ctl->messages;
+ unsigned long ring_size = netconsole_ctl->ring_size;
+ unsigned long head = ACCESS_ONCE(messages->head);
+ unsigned long len;
+
+ while (CIRC_CNT(head, messages->tail, ring_size) >= 1) {
+ /* read index before reading contents at that index */
+ smp_read_barrier_depends();
+
+ /* pick up a length that don't wrap in the middle */
+ len = CIRC_CNT_TO_END(head, messages->tail, ring_size);
+ netconsole_start_xmit(&messages->buf[messages->tail], len);
+
+ /* finish reading descriptor before incrementing tail */
+ smp_mb();
+ messages->tail = RING_INC_POS(messages->tail, len, ring_size);
+ head = ACCESS_ONCE(messages->head);
+ }
+}
+
#ifdef CONFIG_NETCONSOLE_DYNAMIC
static struct configfs_subsystem netconsole_subsys;
@@ -702,38 +777,43 @@ static struct notifier_block netconsole_netdev_notifier = {
.notifier_call = netconsole_netdev_event,
};
+/* called with console sem, interrupts disabled */
static void write_msg(struct console *con, const char *msg, unsigned int len)
{
- int frag, left;
- unsigned long flags;
- struct netconsole_target *nt;
- const char *tmp;
+ struct circ_buf *messages = &netconsole_ctl->messages;
+ unsigned long ring_size = netconsole_ctl->ring_size;
+ unsigned long tail = ACCESS_ONCE(messages->tail);
+ unsigned long left;
+ unsigned long end;
+ unsigned long pos;
/* Avoid taking lock and disabling interrupts unnecessarily */
if (list_empty(&target_list))
return;
- spin_lock_irqsave(&target_list_lock, flags);
- list_for_each_entry(nt, &target_list, list) {
- netconsole_target_get(nt);
- if (nt->enabled && netif_running(nt->np.dev)) {
- /*
- * We nest this inside the for-each-target loop above
- * so that we're able to get as much logging out to
- * at least one target if we die inside here, instead
- * of unnecessarily keeping all targets in lock-step.
- */
- tmp = msg;
- for (left = len; left;) {
- frag = min(left, MAX_PRINT_CHUNK);
- netpoll_send_udp(&nt->np, tmp, frag);
- tmp += frag;
- left -= frag;
- }
+ pos = 0;
+ left = len;
+ while (left && CIRC_SPACE(messages->head, tail, ring_size) >= 1) {
+ end = CIRC_SPACE_TO_END(messages->head, tail, ring_size);
+ /* fast path, no wrapping is needed */
+ if (end >= left) {
+ memcpy(&messages->buf[messages->head], &msg[pos], left);
+ smp_wmb();
+ messages->head = RING_INC_POS(messages->head, left, ring_size);
+ left = 0;
}
- netconsole_target_put(nt);
+ else {
+ /* copy up to the end */
+ memcpy(&messages->buf[messages->head], &msg[pos], end);
+ smp_wmb();
+ messages->head = RING_INC_POS(messages->head, end, ring_size);
+ left -= end;
+ pos += end;
+ }
+
}
- spin_unlock_irqrestore(&target_list_lock, flags);
+
+ schedule_work(&netconsole_ctl->tx_work);
}
static struct console netconsole = {
@@ -746,9 +826,25 @@ static int __init init_netconsole(void)
{
int err;
struct netconsole_target *nt, *tmp;
+ struct circ_buf *messages;
unsigned long flags;
char *target_config;
char *input = config;
+ int order = get_order(logsize);
+
+ err = -ENOMEM;
+ netconsole_ctl = kzalloc(sizeof(*netconsole_ctl), GFP_KERNEL);
+ if (netconsole_ctl == NULL)
+ goto nomem;
+
+ netconsole_ctl->buffer_page = alloc_pages(GFP_KERNEL, order);
+ if (netconsole_ctl->buffer_page == NULL)
+ goto nopage;
+
+ netconsole_ctl->ring_size = (PAGE_SIZE << order);
+ messages = &netconsole_ctl->messages;
+ messages->buf = page_address(netconsole_ctl->buffer_page);
+ INIT_WORK(&netconsole_ctl->tx_work, netconsole_process_queue);
if (strnlen(input, MAX_PARAM_LENGTH)) {
while ((target_config = strsep(&input, ";"))) {
@@ -795,6 +891,11 @@ fail:
free_param_target(nt);
}
+ __free_pages(netconsole_ctl->buffer_page, order);
+nopage:
+ kfree(netconsole_ctl);
+
+nomem:
return err;
}
@@ -806,6 +907,10 @@ static void __exit cleanup_netconsole(void)
dynamic_netconsole_exit();
unregister_netdevice_notifier(&netconsole_netdev_notifier);
+ flush_work(&netconsole_ctl->tx_work);
+ cancel_work_sync(&netconsole_ctl->tx_work);
+ netconsole_process_queue(NULL);
+
/*
* Targets created via configfs pin references on our module
* and would first be rmdir(2)'ed from userspace. We reach
@@ -818,6 +923,11 @@ static void __exit cleanup_netconsole(void)
list_del(&nt->list);
free_param_target(nt);
}
+
+ __free_pages(netconsole_ctl->buffer_page,
+ get_order(netconsole_ctl->ring_size));
+
+ kfree(netconsole_ctl);
}
module_init(init_netconsole);
--
1.7.0.1
--
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