On 05/24, Oleg Nesterov wrote:
>
> audit_log_start() does wait_for_auditd() in a loop until
> audit_backlog_wait_time passes or audit_skb_queue has a room.
>
> If signal_pending() is true this becomes a busy-wait loop,
> schedule() in TASK_INTERRUPTIBLE won't block.
And the code looks strange imho. I think it should be cleanuped,
something like below. But I do not know how can I test this change.
Oleg.
--- x/kernel/audit.c
+++ x/kernel/audit.c
@@ -1053,18 +1053,19 @@ static inline void audit_get_stamp(struc
/*
* Wait for auditd to drain the queue a little
*/
-static void wait_for_auditd(unsigned long sleep_time)
+static bool wait_for_auditd(gfp_t gfp_mask)
{
- DECLARE_WAITQUEUE(wait, current);
- set_current_state(TASK_INTERRUPTIBLE);
- add_wait_queue(&audit_backlog_wait, &wait);
-
- if (audit_backlog_limit &&
- skb_queue_len(&audit_skb_queue) > audit_backlog_limit)
- schedule_timeout(sleep_time);
+ bool can_wait = gfp_mask & __GFP_WAIT;
+ int reserve = can_wait ? 0 : 5;
- __set_current_state(TASK_RUNNING);
- remove_wait_queue(&audit_backlog_wait, &wait);
+ if (!audit_backlog_limit ||
+ skb_queue_len(&audit_skb_queue) <= audit_backlog_limit + reserve)
+ return true;
+
+ return can_wait && wait_event_timeout(audit_backlog_wait,
+ !audit_backlog_limit ||
+ skb_queue_len(&audit_skb_queue) <=
audit_backlog_limit,
+ audit_backlog_wait_time);
}
/* Obtain an audit buffer. This routine does locking to obtain the
@@ -1095,8 +1096,6 @@ struct audit_buffer *audit_log_start(str
struct audit_buffer *ab = NULL;
struct timespec t;
unsigned int uninitialized_var(serial);
- int reserve;
- unsigned long timeout_start = jiffies;
if (audit_initialized != AUDIT_INITIALIZED)
return NULL;
@@ -1104,23 +1103,7 @@ struct audit_buffer *audit_log_start(str
if (unlikely(audit_filter_type(type)))
return NULL;
- if (gfp_mask & __GFP_WAIT)
- reserve = 0;
- else
- reserve = 5; /* Allow atomic callers to go up to five
- entries over the normal backlog limit */
-
- while (audit_backlog_limit
- && skb_queue_len(&audit_skb_queue) > audit_backlog_limit +
reserve) {
- if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time) {
- unsigned long sleep_time;
-
- sleep_time = timeout_start + audit_backlog_wait_time -
- jiffies;
- if ((long)sleep_time > 0)
- wait_for_auditd(sleep_time);
- continue;
- }
+ if (!wait_for_auditd(gfp_mask)) {
if (audit_rate_check() && printk_ratelimit())
printk(KERN_WARNING
"audit: audit_backlog=%d > "
--
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