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Chunyu Hu reported:
"per_cpu trace directories and files are created for all possible cpus,
but only the cpus which have ever been on-lined have their own per cpu
ring buffer (allocated by cpuhp threads). While trace_buffers_open, the
open handler for trace file 'trace_pipe_raw' is always trying to access
field of ring_buffer_per_cpu, and would panic with the NULL pointer.
Align the behavior of trace_pipe_raw with trace_pipe, that returns -NODEV
when openning it if that cpu does not have trace ring buffer.
Reproduce:
cat /sys/kernel/debug/tracing/per_cpu/cpu31/trace_pipe_raw
(cpu31 is never on-lined, this is a 16 cores x86_64 box)
Tested with:
1) boot with maxcpus=14, read trace_pipe_raw of cpu15.
Got -NODEV.
2) oneline cpu15, read trace_pipe_raw of cpu15.
Get the raw trace data.
Call trace:
[ 5760.950995] RIP: 0010:ring_buffer_alloc_read_page+0x32/0xe0
[ 5760.961678] tracing_buffers_read+0x1f6/0x230
[ 5760.962695] __vfs_read+0x37/0x160
[ 5760.963498] ? __vfs_read+0x5/0x160
[ 5760.964339] ? security_file_permission+0x9d/0xc0
[ 5760.965451] ? __vfs_read+0x5/0x160
[ 5760.966280] vfs_read+0x8c/0x130
[ 5760.967070] SyS_read+0x55/0xc0
[ 5760.967779] do_syscall_64+0x67/0x150
[ 5760.968687] entry_SYSCALL64_slow_path+0x25/0x25"
This was introduced by the addition of the feature to reuse reader pages
instead of re-allocating them. The problem is that the allocation of a
reader page (which is per cpu) does not check if the cpu is online and set
up for the ring buffer.
Link: http://lkml.kernel.org/r/1500880866-1177-1-git-send-email-chuhu@redhat.com
Cc: stable@vger.kernel.org
Fixes:
|
||
|---|---|---|
| .. | ||
| blktrace.c | ||
| bpf_trace.c | ||
| ftrace.c | ||
| Kconfig | ||
| Makefile | ||
| power-traces.c | ||
| ring_buffer_benchmark.c | ||
| ring_buffer.c | ||
| rpm-traces.c | ||
| trace_benchmark.c | ||
| trace_benchmark.h | ||
| trace_branch.c | ||
| trace_clock.c | ||
| trace_entries.h | ||
| trace_event_perf.c | ||
| trace_events_filter_test.h | ||
| trace_events_filter.c | ||
| trace_events_hist.c | ||
| trace_events_trigger.c | ||
| trace_events.c | ||
| trace_export.c | ||
| trace_functions_graph.c | ||
| trace_functions.c | ||
| trace_hwlat.c | ||
| trace_irqsoff.c | ||
| trace_kdb.c | ||
| trace_kprobe.c | ||
| trace_mmiotrace.c | ||
| trace_nop.c | ||
| trace_output.c | ||
| trace_output.h | ||
| trace_printk.c | ||
| trace_probe.c | ||
| trace_probe.h | ||
| trace_sched_switch.c | ||
| trace_sched_wakeup.c | ||
| trace_selftest_dynamic.c | ||
| trace_selftest.c | ||
| trace_seq.c | ||
| trace_stack.c | ||
| trace_stat.c | ||
| trace_stat.h | ||
| trace_syscalls.c | ||
| trace_uprobe.c | ||
| trace.c | ||
| trace.h | ||
| tracing_map.c | ||
| tracing_map.h | ||