Rabin Vincent e30f53aad2 tracing: Do not busy wait in buffer splice ... On a !PREEMPT kernel, attempting to use trace-cmd results in a soft lockup: # trace-cmd record -e raw_syscalls:* -F false NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [trace-cmd:61] ... Call Trace: [<ffffffff8105b580>] ? __wake_up_common+0x90/0x90 [<ffffffff81092e25>] wait_on_pipe+0x35/0x40 [<ffffffff810936e3>] tracing_buffers_splice_read+0x2e3/0x3c0 [<ffffffff81093300>] ? tracing_stats_read+0x2a0/0x2a0 [<ffffffff812d10ab>] ? _raw_spin_unlock+0x2b/0x40 [<ffffffff810dc87b>] ? do_read_fault+0x21b/0x290 [<ffffffff810de56a>] ? handle_mm_fault+0x2ba/0xbd0 [<ffffffff81095c80>] ? trace_event_buffer_lock_reserve+0x40/0x80 [<ffffffff810951e2>] ? trace_buffer_lock_reserve+0x22/0x60 [<ffffffff81095c80>] ? trace_event_buffer_lock_reserve+0x40/0x80 [<ffffffff8112415d>] do_splice_to+0x6d/0x90 [<ffffffff81126971>] SyS_splice+0x7c1/0x800 [<ffffffff812d1edd>] tracesys_phase2+0xd3/0xd8 The problem is this: tracing_buffers_splice_read() calls ring_buffer_wait() to wait for data in the ring buffers. The buffers are not empty so ring_buffer_wait() returns immediately. But tracing_buffers_splice_read() calls ring_buffer_read_page() with full=1, meaning it only wants to read a full page. When the full page is not available, tracing_buffers_splice_read() tries to wait again with ring_buffer_wait(), which again returns immediately, and so on. Fix this by adding a "full" argument to ring_buffer_wait() which will make ring_buffer_wait() wait until the writer has left the reader's page, i.e. until full-page reads will succeed. Link: http://lkml.kernel.org/r/1415645194-25379-1-git-send-email-rabin@rab.in Cc: stable@vger.kernel.org # 3.16+ Fixes: b1169cc69b ("tracing: Remove mock up poll wait function") Signed-off-by: Rabin Vincent <rabin@rab.in> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>		2014-11-10 16:45:43 -05:00
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blktrace.c
ftrace.c	ftrace: Fix checking of trampoline ftrace_ops in finding trampoline	2014-10-24 16:53:11 -04:00
Kconfig
Makefile
power-traces.c
ring_buffer_benchmark.c
ring_buffer.c	tracing: Do not busy wait in buffer splice	2014-11-10 16:45:43 -05:00
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_trigger.c
trace_events.c	tracing: Robustify wait loop	2014-10-08 19:51:01 -04:00
trace_export.c
trace_functions_graph.c
trace_functions.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	Seems that Peter Zijlstra added a new check that is making old	2014-10-12 07:28:55 -04:00
trace_seq.c
trace_stack.c	sched: Add helper for task stack page overrun checking	2014-09-19 12:35:23 +02:00
trace_stat.c
trace_stat.h
trace_syscalls.c	tracing/syscalls: Ignore numbers outside NR_syscalls' range	2014-10-30 20:58:38 -04:00
trace_uprobe.c
trace.c	tracing: Do not busy wait in buffer splice	2014-11-10 16:45:43 -05:00
trace.h