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a33614d52e
commit aafe104aa9096827a429bc1358f8260ee565b7cc upstream.
It was reported that a fix to the ring buffer recursion detection would
cause a hung machine when performing suspend / resume testing. The
following backtrace was extracted from debugging that case:
Call Trace:
trace_clock_global+0x91/0xa0
__rb_reserve_next+0x237/0x460
ring_buffer_lock_reserve+0x12a/0x3f0
trace_buffer_lock_reserve+0x10/0x50
__trace_graph_return+0x1f/0x80
trace_graph_return+0xb7/0xf0
? trace_clock_global+0x91/0xa0
ftrace_return_to_handler+0x8b/0xf0
? pv_hash+0xa0/0xa0
return_to_handler+0x15/0x30
? ftrace_graph_caller+0xa0/0xa0
? trace_clock_global+0x91/0xa0
? __rb_reserve_next+0x237/0x460
? ring_buffer_lock_reserve+0x12a/0x3f0
? trace_event_buffer_lock_reserve+0x3c/0x120
? trace_event_buffer_reserve+0x6b/0xc0
? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0
? dpm_run_callback+0x3b/0xc0
? pm_ops_is_empty+0x50/0x50
? platform_get_irq_byname_optional+0x90/0x90
? trace_device_pm_callback_start+0x82/0xd0
? dpm_run_callback+0x49/0xc0
With the following RIP:
RIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200
Since the fix to the recursion detection would allow a single recursion to
happen while tracing, this lead to the trace_clock_global() taking a spin
lock and then trying to take it again:
ring_buffer_lock_reserve() {
trace_clock_global() {
arch_spin_lock() {
queued_spin_lock_slowpath() {
/* lock taken */
(something else gets traced by function graph tracer)
ring_buffer_lock_reserve() {
trace_clock_global() {
arch_spin_lock() {
queued_spin_lock_slowpath() {
/* DEAD LOCK! */
Tracing should *never* block, as it can lead to strange lockups like the
above.
Restructure the trace_clock_global() code to instead of simply taking a
lock to update the recorded "prev_time" simply use it, as two events
happening on two different CPUs that calls this at the same time, really
doesn't matter which one goes first. Use a trylock to grab the lock for
updating the prev_time, and if it fails, simply try again the next time.
If it failed to be taken, that means something else is already updating
it.
Link: https://lkml.kernel.org/r/20210430121758.650b6e8a@gandalf.local.home
Cc: stable@vger.kernel.org
Tested-by: Konstantin Kharlamov <hi-angel@yandex.ru>
Tested-by: Todd Brandt <todd.e.brandt@linux.intel.com>
Fixes:
|
||
|---|---|---|
| .. | ||
| blktrace.c | ||
| bpf_trace.c | ||
| bpf_trace.h | ||
| fgraph.c | ||
| ftrace_internal.h | ||
| ftrace.c | ||
| Kconfig | ||
| kprobe_event_gen_test.c | ||
| Makefile | ||
| power-traces.c | ||
| preemptirq_delay_test.c | ||
| ring_buffer_benchmark.c | ||
| ring_buffer.c | ||
| rpm-traces.c | ||
| synth_event_gen_test.c | ||
| trace_benchmark.c | ||
| trace_benchmark.h | ||
| trace_boot.c | ||
| trace_branch.c | ||
| trace_clock.c | ||
| trace_dynevent.c | ||
| trace_dynevent.h | ||
| trace_entries.h | ||
| trace_event_perf.c | ||
| trace_events_filter_test.h | ||
| trace_events_filter.c | ||
| trace_events_hist.c | ||
| trace_events_inject.c | ||
| trace_events_synth.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_selftest.c | ||
| trace_kprobe_selftest.h | ||
| trace_kprobe.c | ||
| trace_mmiotrace.c | ||
| trace_nop.c | ||
| trace_output.c | ||
| trace_output.h | ||
| trace_preemptirq.c | ||
| trace_printk.c | ||
| trace_probe_tmpl.h | ||
| 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_synth.h | ||
| trace_syscalls.c | ||
| trace_uprobe.c | ||
| trace.c | ||
| trace.h | ||
| tracing_map.c | ||
| tracing_map.h | ||