| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Mon, 26 Oct 2015 05:52:45 +0100
From: Jan Kara <jack@...e.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>, pmladek@...e.com,
KY Srinivasan <kys@...rosoft.com>, rostedt@...dmis.org,
Jan Kara <jack@...e.cz>
Subject: [PATCH 2/7] printk: Start printing handover kthreads on demand
From: Jan Kara <jack@...e.cz>
Start kthreads for handing over printing only when printk.offload_chars
is set to value > 0 (i.e., when print offloading gets enabled).
Signed-off-by: Jan Kara <jack@...e.cz>
---
kernel/printk/printk.c | 78 +++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 64 insertions(+), 14 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 1b26263edfa7..b9bb4a7a6dff 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -98,6 +98,10 @@ static atomic_t printing_tasks_spinning = ATOMIC_INIT(0);
* CPUs.
*/
#define PRINTING_TASKS 2
+/* Pointers to printing kthreads */
+static struct task_struct *printing_kthread[PRINTING_TASKS];
+/* Serialization of changes to printk_offload_chars and kthread creation */
+static DEFINE_MUTEX(printk_kthread_mutex);
/* Wait queue printing kthreads sleep on when idle */
static DECLARE_WAIT_QUEUE_HEAD(print_queue);
@@ -303,6 +307,13 @@ static u32 clear_idx;
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
static char *log_buf = __log_buf;
static u32 log_buf_len = __LOG_BUF_LEN;
+
+static int offload_chars_set(const char *val, const struct kernel_param *kp);
+static struct kernel_param_ops offload_chars_ops = {
+ .set = offload_chars_set,
+ .get = param_get_uint,
+};
+
/*
* How many characters can we print in one call of printk before asking
* other cpus to continue printing. 0 means infinity. Tunable via
@@ -311,7 +322,7 @@ static u32 log_buf_len = __LOG_BUF_LEN;
*/
static unsigned int __read_mostly printk_offload_chars = 1000;
-module_param_named(offload_chars, printk_offload_chars, uint,
+module_param_cb(offload_chars, &offload_chars_ops, &printk_offload_chars,
S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(offload_chars, "offload printing to console to a different"
" cpu after this number of characters");
@@ -2778,12 +2789,61 @@ static int printing_task(void *arg)
return 0;
}
-static int __init printk_late_init(void)
+static int printk_start_offload_kthreads(void)
{
- struct console *con;
int i;
struct task_struct *task;
+ /* Does handover of printing make any sense? */
+ if (printk_offload_chars == 0 || num_possible_cpus() <= 1)
+ return 0;
+ for (i = 0; i < PRINTING_TASKS; i++) {
+ if (printing_kthread[i])
+ continue;
+ task = kthread_run(printing_task, NULL, "print/%d", i);
+ if (IS_ERR(task))
+ goto out_err;
+ printing_kthread[i] = task;
+ }
+ return 0;
+out_err:
+ pr_err("printk: Cannot create printing thread: %ld\n", PTR_ERR(task));
+ /* Disable offloading if creating kthreads failed */
+ printk_offload_chars = 0;
+ return PTR_ERR(task);
+}
+
+static int offload_chars_set(const char *val, const struct kernel_param *kp)
+{
+ int ret;
+
+ /* Protect against parallel change of printk_offload_chars */
+ mutex_lock(&printk_kthread_mutex);
+ ret = param_set_uint(val, kp);
+ if (ret) {
+ mutex_unlock(&printk_kthread_mutex);
+ return ret;
+ }
+ ret = printk_start_offload_kthreads();
+ mutex_unlock(&printk_kthread_mutex);
+ return ret;
+}
+
+static void printk_offload_init(void)
+{
+ mutex_lock(&printk_kthread_mutex);
+ if (num_possible_cpus() <= 1) {
+ /* Offloading doesn't make sense. Disable print offloading. */
+ printk_offload_chars = 0;
+ } else
+ printk_start_offload_kthreads();
+ mutex_unlock(&printk_kthread_mutex);
+}
+
+static int __init printk_late_init(void)
+{
+ struct console *con;
+
for_each_console(con) {
if (!keep_bootcon && con->flags & CON_BOOT) {
unregister_console(con);
@@ -2791,17 +2851,7 @@ static int __init printk_late_init(void)
}
hotcpu_notifier(console_cpu_notify, 0);
- /* Does any handover of printing have any sence? */
- if (num_possible_cpus() <= 1)
- return 0;
-
- for (i = 0; i < PRINTING_TASKS; i++) {
- task = kthread_run(printing_task, NULL, "print/%d", i);
- if (IS_ERR(task)) {
- pr_err("printk: Cannot create printing thread: %ld\n",
- PTR_ERR(task));
- }
- }
+ printk_offload_init();
return 0;
}
--
2.1.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists