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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-02-22 01:12:47 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-02-22 01:12:47 -0300
commit6d461a4fe7896faa1aec5a5417888cf179e46b9f (patch)
tree2e0f1a0b7a5418189c8d53592d33a44d0b356fc9 /kernel/printk
parent5c545e1fb127a4b11ddc5f1a5ed066b853dd1a1a (diff)
Linux-libre 4.4.2-gnupck-4.4.2-gnu
Diffstat (limited to 'kernel/printk')
-rw-r--r--kernel/printk/printk.c35
1 files changed, 34 insertions, 1 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index f9b746700..8362f1979 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2248,13 +2248,24 @@ void console_unlock(void)
static u64 seen_seq;
unsigned long flags;
bool wake_klogd = false;
- bool retry;
+ bool do_cond_resched, retry;
if (console_suspended) {
up_console_sem();
return;
}
+ /*
+ * Console drivers are called under logbuf_lock, so
+ * @console_may_schedule should be cleared before; however, we may
+ * end up dumping a lot of lines, for example, if called from
+ * console registration path, and should invoke cond_resched()
+ * between lines if allowable. Not doing so can cause a very long
+ * scheduling stall on a slow console leading to RCU stall and
+ * softlockup warnings which exacerbate the issue with more
+ * messages practically incapacitating the system.
+ */
+ do_cond_resched = console_may_schedule;
console_may_schedule = 0;
/* flush buffered message fragment immediately to console */
@@ -2326,6 +2337,9 @@ skip:
call_console_drivers(level, ext_text, ext_len, text, len);
start_critical_timings();
local_irq_restore(flags);
+
+ if (do_cond_resched)
+ cond_resched();
}
console_locked = 0;
@@ -2393,6 +2407,25 @@ void console_unblank(void)
console_unlock();
}
+/**
+ * console_flush_on_panic - flush console content on panic
+ *
+ * Immediately output all pending messages no matter what.
+ */
+void console_flush_on_panic(void)
+{
+ /*
+ * If someone else is holding the console lock, trylock will fail
+ * and may_schedule may be set. Ignore and proceed to unlock so
+ * that messages are flushed out. As this can be called from any
+ * context and we don't want to get preempted while flushing,
+ * ensure may_schedule is cleared.
+ */
+ console_trylock();
+ console_may_schedule = 0;
+ console_unlock();
+}
+
/*
* Return the console tty driver structure and its associated index
*/