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| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2021-12-13 11:08:53 +0100 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2022-01-13 16:23:04 -0500 |
| commit | 289e7b0f7eb47b87a0441e6c81336316f301eb39 (patch) | |
| tree | 48538debf71756dd4b53ceabde05da71bc63b440 | |
| parent | 86599dbe2c5272588f859858239d1f52321eb0f9 (diff) | |
| download | linux-289e7b0f7eb47b87a0441e6c81336316f301eb39.tar.gz linux-289e7b0f7eb47b87a0441e6c81336316f301eb39.tar.bz2 linux-289e7b0f7eb47b87a0441e6c81336316f301eb39.zip | |
tracing: Account bottom half disabled sections.
Disabling only bottom halves via local_bh_disable() disables also
preemption but this remains invisible to tracing. On a CONFIG_PREEMPT
kernel one might wonder why there is no scheduling happening despite the
N flag in the trace. The reason might be the a rcu_read_lock_bh()
section.
Add a 'b' to the tracing output if in task context with disabled bottom
halves.
Link: https://lkml.kernel.org/r/YbcbtdtC/bjCKo57@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
| -rw-r--r-- | include/linux/trace_events.h | 1 | ||||
| -rw-r--r-- | kernel/trace/trace.c | 6 | ||||
| -rw-r--r-- | kernel/trace/trace_output.c | 4 |
3 files changed, 9 insertions, 2 deletions
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 3900404aa063..70c069aef02c 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -172,6 +172,7 @@ enum trace_flag_type { TRACE_FLAG_SOFTIRQ = 0x10, TRACE_FLAG_PREEMPT_RESCHED = 0x20, TRACE_FLAG_NMI = 0x40, + TRACE_FLAG_BH_OFF = 0x80, }; #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 547d82628c2e..a73d78dcda2c 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2603,6 +2603,8 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status) trace_flags |= TRACE_FLAG_HARDIRQ; if (in_serving_softirq()) trace_flags |= TRACE_FLAG_SOFTIRQ; + if (softirq_count() >> (SOFTIRQ_SHIFT + 1)) + trace_flags |= TRACE_FLAG_BH_OFF; if (tif_need_resched()) trace_flags |= TRACE_FLAG_NEED_RESCHED; @@ -4190,7 +4192,7 @@ unsigned long trace_total_entries(struct trace_array *tr) static void print_lat_help_header(struct seq_file *m) { seq_puts(m, "# _------=> CPU# \n" - "# / _-----=> irqs-off \n" + "# / _-----=> irqs-off/BH-disabled\n" "# | / _----=> need-resched \n" "# || / _---=> hardirq/softirq \n" "# ||| / _--=> preempt-depth \n" @@ -4231,7 +4233,7 @@ static void print_func_help_header_irq(struct array_buffer *buf, struct seq_file print_event_info(buf, m); - seq_printf(m, "# %.*s _-----=> irqs-off\n", prec, space); + seq_printf(m, "# %.*s _-----=> irqs-off/BH-disabled\n", prec, space); seq_printf(m, "# %.*s / _----=> need-resched\n", prec, space); seq_printf(m, "# %.*s| / _---=> hardirq/softirq\n", prec, space); seq_printf(m, "# %.*s|| / _--=> preempt-depth\n", prec, space); diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 3547e7176ff7..8aa493d25c73 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -445,14 +445,18 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry) char irqs_off; int hardirq; int softirq; + int bh_off; int nmi; nmi = entry->flags & TRACE_FLAG_NMI; hardirq = entry->flags & TRACE_FLAG_HARDIRQ; softirq = entry->flags & TRACE_FLAG_SOFTIRQ; + bh_off = entry->flags & TRACE_FLAG_BH_OFF; irqs_off = + (entry->flags & TRACE_FLAG_IRQS_OFF && bh_off) ? 'D' : (entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' : + bh_off ? 'b' : (entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' : '.'; |