Messages in this thread | | | Subject | Re: [ring_buffer_entries] BUG: unable to handle kernel NULL pointer dereference at (null) | From | Steven Rostedt <> | Date | Wed, 29 May 2013 15:36:24 -0400 |
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On Wed, 2013-05-29 at 22:13 +0800, Fengguang Wu wrote: > Hi Rostedt, > > I got the below BUG and the first bad commit could be any of: > > ce9bae55972b228cf7bac34350c4d2caf8ea0d0b > 121aaee7b0a82605d33af200c7e9ebab6fd6e444 > 737223fbca3b1c91feb947c7f571b35749b743b6 > 45ad21ca5530efdca6a19e4a5ac5e7bd6e24f996 > a695cb5816228f86576f5f5c6809fdf8ed382ece > 6de58e6269cd0568ca5fbae14423914eff0f7811 > ad909e21bbe69f1d39055d346540abd827190eca > 0b85ffc293044393623059eda9904a7d5b644e36 > f5eb5588262cab7232ed1d77cf612b327db50767 > f1affcaaa861f27752a769f889bf1486ebd301fe > f4e781c0a89d5810729772290441ac7d61f321ec > 12883efb670c28dff57dcd7f4f995a1ffe153b2d > 55034cd6e648155393b0d665eef76b38d49ad6bf > 153e8ed913b022d2003866a848af9fadc041403f > > We cannot bisect more due to broken builds.
No need to bisect. The bug is pretty obvious:
$ grep trace_test_buffer kernel/trace/trace_selftest.c static int trace_test_buffer_cpu(struct trace_buffer *buf, int cpu) static int trace_test_buffer(struct trace_buffer *buf, unsigned long *count) * The trace_test_buffer_cpu runs a while loop to consume all data. ret = trace_test_buffer_cpu(buf, cpu); ret = trace_test_buffer(&tr->trace_buffer, &count); ret = trace_test_buffer(&tr->trace_buffer, &count); ret = trace_test_buffer(&tr->trace_buffer, &count); ret = trace_test_buffer(&tr->trace_buffer, &count); ret = trace_test_buffer(&tr->trace_buffer, NULL); ret = trace_test_buffer(&tr->max_buffer, &count); ret = trace_test_buffer(&tr->trace_buffer, NULL); ret = trace_test_buffer(&tr->max_buffer, &count); ret = trace_test_buffer(&tr->trace_buffer, NULL); ret = trace_test_buffer(&tr->max_buffer, &count); ret = trace_test_buffer(&tr->trace_buffer, NULL); ret = trace_test_buffer(&tr->max_buffer, &count); ret = trace_test_buffer(&tr->trace_buffer, NULL); ret = trace_test_buffer(&tr->max_buffer, &count); ret = trace_test_buffer(&tr->trace_buffer, &count); ret = trace_test_buffer(tr, &count);
Notice that all but the last one passes in &tr->trace_buffer or &tr->max_buffer. That last one happens to be in: trace_selftest_startup_branch()
Thanks!
-- Steve
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