Rate limit debugging stack traces

There have been issues in the past where excessive debug logging
to the console has resulted in significant performance impacts.
In the vast majority of these cases only a few stack traces are
required to diagnose the issue.  Therefore, stack traces dumped to
the console will now we limited to 5 every 60s.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Closes #374

diff --git a/module/spl/spl-debug.c b/module/spl/spl-debug.c
index 93c3f31b8a2604327584be855eaec0977a0c3ba6..6c4e043f05da70b0d872fab1fa840d0448f696c4 100644 (file)
--- a/module/spl/spl-debug.c
+++ b/module/spl/spl-debug.c
@@ -37,6 +37,7 @@
 #include <linux/proc_compat.h>
 #include <linux/file_compat.h>
 #include <linux/swap.h>
+#include <linux/ratelimit.h>
 #include <sys/sysmacros.h>
 #include <sys/thread.h>
 #include <spl-debug.h>
@@ -1073,15 +1074,22 @@ spl_debug_get_mb(void)
 }
 EXPORT_SYMBOL(spl_debug_get_mb);
 
-void spl_debug_dumpstack(struct task_struct *tsk)
-{
-        extern void show_task(struct task_struct *);
+/*
+ * Limit the number of stack traces dumped to not more than 5 every
+ * 60 seconds to prevent denial-of-service attacks from debug code.
+ */
+DEFINE_RATELIMIT_STATE(dumpstack_ratelimit_state, 60 * HZ, 5);
 
-        if (tsk == NULL)
-                tsk = current;
+void
+spl_debug_dumpstack(struct task_struct *tsk)
+{
+       if (__ratelimit(&dumpstack_ratelimit_state)) {
+               if (tsk == NULL)
+                       tsk = current;
 
-        printk("SPL: Showing stack for process %d\n", tsk->pid);
-        dump_stack();
+               printk("SPL: Showing stack for process %d\n", tsk->pid);
+               dump_stack();
+       }
 }
 EXPORT_SYMBOL(spl_debug_dumpstack);
 

diff --git a/module/spl/spl-kmem.c b/module/spl/spl-kmem.c
index e458c202013143d5fdf570007539adc9e55f542d..6389dc5aaba76086cc368d844df216b95c942533 100644 (file)
--- a/module/spl/spl-kmem.c
+++ b/module/spl/spl-kmem.c
@@ -725,7 +725,7 @@ kmem_alloc_debug(size_t size, int flags, const char *func, int line,
                    "large kmem_alloc(%llu, 0x%x) at %s:%d (%lld/%llu)\n",
                    (unsigned long long) size, flags, func, line,
                    kmem_alloc_used_read(), kmem_alloc_max);
-               dump_stack();
+               spl_debug_dumpstack(NULL);
        }
 
        /* Use the correct allocator */