Merge git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-2.6-nmw

[cascardo/linux.git] / kernel / trace / trace.c

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 82d9b81..f8cf959 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -17,7 +17,6 @@
 #include <linux/writeback.h>
 #include <linux/kallsyms.h>
 #include <linux/seq_file.h>
-#include <linux/smp_lock.h>
 #include <linux/notifier.h>
 #include <linux/irqflags.h>
 #include <linux/debugfs.h>
@@ -1284,6 +1283,8 @@ void trace_dump_stack(void)
        __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count());
 }
 
+static DEFINE_PER_CPU(int, user_stack_count);
+
 void
 ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
 {
@@ -1302,6 +1303,18 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
        if (unlikely(in_nmi()))
                return;
 
+       /*
+        * prevent recursion, since the user stack tracing may
+        * trigger other kernel events.
+        */
+       preempt_disable();
+       if (__this_cpu_read(user_stack_count))
+               goto out;
+
+       __this_cpu_inc(user_stack_count);
+
+
+
        event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,
                                          sizeof(*entry), flags, pc);
        if (!event)
@@ -1319,6 +1332,11 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
        save_stack_trace_user(&trace);
        if (!filter_check_discard(call, entry, buffer, event))
                ring_buffer_unlock_commit(buffer, event);
+
+       __this_cpu_dec(user_stack_count);
+
+ out:
+       preempt_enable();
 }
 
 #ifdef UNUSED
@@ -2320,11 +2338,19 @@ tracing_write_stub(struct file *filp, const char __user *ubuf,
        return count;
 }
 
+static loff_t tracing_seek(struct file *file, loff_t offset, int origin)
+{
+       if (file->f_mode & FMODE_READ)
+               return seq_lseek(file, offset, origin);
+       else
+               return 0;
+}
+
 static const struct file_operations tracing_fops = {
        .open           = tracing_open,
        .read           = seq_read,
        .write          = tracing_write_stub,
-       .llseek         = seq_lseek,
+       .llseek         = tracing_seek,
        .release        = tracing_release,
 };