8520dedbbf
Currently kdb's ftdump command will livelock by constantly printk'ing the empty string at KERN_EMERG level if it run when the ftrace system is not in use. This occurs because trace_empty() never returns false when the ring buffers are left at the start of a non-consuming read [launched by ring_buffer_read_start()]. This patch changes the loop exit condition to use the result of trace_find_next_entry_inc(). Effectively this switches the non-consuming kdb dumper to follow the approach of the non-consuming userspace interface [s_next()] rather than the consuming ftrace_dump(). Link: http://lkml.kernel.org/r/1415277716-19419-3-git-send-email-daniel.thompson@linaro.org Cc: Ingo Molnar <mingo@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Jason Wessel <jason.wessel@windriver.com> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
140 lines
3.1 KiB
C
140 lines
3.1 KiB
C
/*
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* kdb helper for dumping the ftrace buffer
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*
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* Copyright (C) 2010 Jason Wessel <jason.wessel@windriver.com>
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*
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* ftrace_dump_buf based on ftrace_dump:
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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* Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
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*
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*/
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#include <linux/init.h>
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#include <linux/kgdb.h>
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#include <linux/kdb.h>
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#include <linux/ftrace.h>
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#include "trace.h"
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#include "trace_output.h"
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static void ftrace_dump_buf(int skip_lines, long cpu_file)
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{
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/* use static because iter can be a bit big for the stack */
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static struct trace_iterator iter;
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static struct ring_buffer_iter *buffer_iter[CONFIG_NR_CPUS];
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unsigned int old_userobj;
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int cnt = 0, cpu;
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trace_init_global_iter(&iter);
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iter.buffer_iter = buffer_iter;
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for_each_tracing_cpu(cpu) {
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atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
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}
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old_userobj = trace_flags;
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/* don't look at user memory in panic mode */
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trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
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kdb_printf("Dumping ftrace buffer:\n");
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/* reset all but tr, trace, and overruns */
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memset(&iter.seq, 0,
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sizeof(struct trace_iterator) -
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offsetof(struct trace_iterator, seq));
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iter.iter_flags |= TRACE_FILE_LAT_FMT;
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iter.pos = -1;
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if (cpu_file == RING_BUFFER_ALL_CPUS) {
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for_each_tracing_cpu(cpu) {
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iter.buffer_iter[cpu] =
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ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu);
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ring_buffer_read_start(iter.buffer_iter[cpu]);
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tracing_iter_reset(&iter, cpu);
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}
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} else {
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iter.cpu_file = cpu_file;
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iter.buffer_iter[cpu_file] =
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ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu_file);
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ring_buffer_read_start(iter.buffer_iter[cpu_file]);
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tracing_iter_reset(&iter, cpu_file);
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}
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while (trace_find_next_entry_inc(&iter)) {
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if (!cnt)
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kdb_printf("---------------------------------\n");
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cnt++;
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if (!skip_lines) {
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print_trace_line(&iter);
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trace_printk_seq(&iter.seq);
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} else {
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skip_lines--;
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}
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if (KDB_FLAG(CMD_INTERRUPT))
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goto out;
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}
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if (!cnt)
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kdb_printf(" (ftrace buffer empty)\n");
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else
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kdb_printf("---------------------------------\n");
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out:
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trace_flags = old_userobj;
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for_each_tracing_cpu(cpu) {
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atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
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}
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for_each_tracing_cpu(cpu) {
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if (iter.buffer_iter[cpu]) {
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ring_buffer_read_finish(iter.buffer_iter[cpu]);
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iter.buffer_iter[cpu] = NULL;
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}
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}
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}
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/*
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* kdb_ftdump - Dump the ftrace log buffer
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*/
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static int kdb_ftdump(int argc, const char **argv)
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{
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int skip_lines = 0;
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long cpu_file;
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char *cp;
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if (argc > 2)
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return KDB_ARGCOUNT;
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if (argc) {
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skip_lines = simple_strtol(argv[1], &cp, 0);
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if (*cp)
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skip_lines = 0;
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}
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if (argc == 2) {
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cpu_file = simple_strtol(argv[2], &cp, 0);
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if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
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!cpu_online(cpu_file))
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return KDB_BADINT;
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} else {
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cpu_file = RING_BUFFER_ALL_CPUS;
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}
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kdb_trap_printk++;
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ftrace_dump_buf(skip_lines, cpu_file);
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kdb_trap_printk--;
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return 0;
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}
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static __init int kdb_ftrace_register(void)
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{
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kdb_register_repeat("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
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"Dump ftrace log", 0, KDB_REPEAT_NONE);
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return 0;
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}
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late_initcall(kdb_ftrace_register);
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