From: Steven Rostedt (Google) rostedt@goodmis.org
[ Upstream commit 00cf3d672a9dd409418647e9f98784c339c3ff63 ]
Allow a stacktrace from one event to be displayed by the end event of a synthetic event. This is very useful when looking for the longest latency of a sleep or something blocked on I/O.
# cd /sys/kernel/tracing/ # echo 's:block_lat pid_t pid; u64 delta; unsigned long[] stack;' > dynamic_events # echo 'hist:keys=next_pid:ts=common_timestamp.usecs,st=stacktrace if prev_state == 1||prev_state == 2' > events/sched/sched_switch/trigger # echo 'hist:keys=prev_pid:delta=common_timestamp.usecs-$ts,s=$st:onmax($delta).trace(block_lat,prev_pid,$delta,$s)' >> events/sched/sched_switch/trigger
The above creates a "block_lat" synthetic event that take the stacktrace of when a task schedules out in either the interruptible or uninterruptible states, and on a new per process max $delta (the time it was scheduled out), will print the process id and the stacktrace.
# echo 1 > events/synthetic/block_lat/enable # cat trace # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | kworker/u16:0-767 [006] d..4. 560.645045: block_lat: pid=767 delta=66 stack=STACK: => __schedule => schedule => pipe_read => vfs_read => ksys_read => do_syscall_64 => 0x966000aa
<idle>-0 [003] d..4. 561.132117: block_lat: pid=0 delta=413787 stack=STACK: => __schedule => schedule => schedule_hrtimeout_range_clock => do_sys_poll => __x64_sys_poll => do_syscall_64 => 0x966000aa
<...>-153 [006] d..4. 562.068407: block_lat: pid=153 delta=54 stack=STACK: => __schedule => schedule => io_schedule => rq_qos_wait => wbt_wait => __rq_qos_throttle => blk_mq_submit_bio => submit_bio_noacct_nocheck => ext4_bio_write_page => mpage_submit_page => mpage_process_page_bufs => mpage_prepare_extent_to_map => ext4_do_writepages => ext4_writepages => do_writepages => __writeback_single_inode
Link: https://lkml.kernel.org/r/20230117152236.010941267@goodmis.org
Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Andrew Morton akpm@linux-foundation.org Cc: Tom Zanussi zanussi@kernel.org Cc: Ross Zwisler zwisler@google.com Cc: Ching-lin Yu chinglinyu@google.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Stable-dep-of: 797311bce5c2 ("tracing/probes: Fix to record 0-length data_loc in fetch_store_string*() if fails") Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/trace.h | 4 ++ kernel/trace/trace_events_hist.c | 7 ++- kernel/trace/trace_events_synth.c | 80 ++++++++++++++++++++++++++++++- kernel/trace/trace_synth.h | 1 + 4 files changed, 87 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index ac7af03ce8372..e90c7e840320d 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -113,6 +113,10 @@ enum trace_type { #define MEM_FAIL(condition, fmt, ...) \ DO_ONCE_LITE_IF(condition, pr_err, "ERROR: " fmt, ##__VA_ARGS__)
+#define HIST_STACKTRACE_DEPTH 16 +#define HIST_STACKTRACE_SIZE (HIST_STACKTRACE_DEPTH * sizeof(unsigned long)) +#define HIST_STACKTRACE_SKIP 5 + /* * syscalls are special, and need special handling, this is why * they are not included in trace_entries.h diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 0f5d16eabd3b0..1470af2190735 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -479,10 +479,6 @@ DEFINE_HIST_FIELD_FN(u8); #define for_each_hist_key_field(i, hist_data) \ for ((i) = (hist_data)->n_vals; (i) < (hist_data)->n_fields; (i)++)
-#define HIST_STACKTRACE_DEPTH 16 -#define HIST_STACKTRACE_SIZE (HIST_STACKTRACE_DEPTH * sizeof(unsigned long)) -#define HIST_STACKTRACE_SKIP 5 - #define HITCOUNT_IDX 0 #define HIST_KEY_SIZE_MAX (MAX_FILTER_STR_VAL + HIST_STACKTRACE_SIZE)
@@ -3843,6 +3839,9 @@ static int check_synth_field(struct synth_event *event, && field->is_dynamic) return 0;
+ if (strstr(hist_field->type, "long[") && field->is_stack) + return 0; + if (strcmp(field->type, hist_field->type) != 0) { if (field->size != hist_field->size || (!field->is_string && field->is_signed != hist_field->is_signed)) diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index 89083ae1aebe3..3c18e7bd40189 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -184,6 +184,14 @@ static int synth_field_is_string(char *type) return false; }
+static int synth_field_is_stack(char *type) +{ + if (strstr(type, "long[") != NULL) + return true; + + return false; +} + static int synth_field_string_size(char *type) { char buf[4], *end, *start; @@ -259,6 +267,8 @@ static int synth_field_size(char *type) size = sizeof(gfp_t); else if (synth_field_is_string(type)) size = synth_field_string_size(type); + else if (synth_field_is_stack(type)) + size = 0;
return size; } @@ -303,6 +313,8 @@ static const char *synth_field_fmt(char *type) fmt = "%x"; else if (synth_field_is_string(type)) fmt = "%.*s"; + else if (synth_field_is_stack(type)) + fmt = "%s";
return fmt; } @@ -382,6 +394,23 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter, i == se->n_fields - 1 ? "" : " "); n_u64 += STR_VAR_LEN_MAX / sizeof(u64); } + } else if (se->fields[i]->is_stack) { + u32 offset, data_offset, len; + unsigned long *p, *end; + + offset = (u32)entry->fields[n_u64]; + data_offset = offset & 0xffff; + len = offset >> 16; + + p = (void *)entry + data_offset; + end = (void *)p + len - (sizeof(long) - 1); + + trace_seq_printf(s, "%s=STACK:\n", se->fields[i]->name); + + for (; *p && p < end; p++) + trace_seq_printf(s, "=> %pS\n", (void *)*p); + n_u64++; + } else { struct trace_print_flags __flags[] = { __def_gfpflag_names, {-1, NULL} }; @@ -458,6 +487,43 @@ static unsigned int trace_string(struct synth_trace_event *entry, return len; }
+static unsigned int trace_stack(struct synth_trace_event *entry, + struct synth_event *event, + long *stack, + unsigned int data_size, + unsigned int *n_u64) +{ + unsigned int len; + u32 data_offset; + void *data_loc; + + data_offset = struct_size(entry, fields, event->n_u64); + data_offset += data_size; + + for (len = 0; len < HIST_STACKTRACE_DEPTH; len++) { + if (!stack[len]) + break; + } + + /* Include the zero'd element if it fits */ + if (len < HIST_STACKTRACE_DEPTH) + len++; + + len *= sizeof(long); + + /* Find the dynamic section to copy the stack into. */ + data_loc = (void *)entry + data_offset; + memcpy(data_loc, stack, len); + + /* Fill in the field that holds the offset/len combo */ + data_offset |= len << 16; + *(u32 *)&entry->fields[*n_u64] = data_offset; + + (*n_u64)++; + + return len; +} + static notrace void trace_event_raw_event_synth(void *__data, u64 *var_ref_vals, unsigned int *var_ref_idx) @@ -510,6 +576,12 @@ static notrace void trace_event_raw_event_synth(void *__data, event->fields[i]->is_dynamic, data_size, &n_u64); data_size += len; /* only dynamic string increments */ + } if (event->fields[i]->is_stack) { + long *stack = (long *)(long)var_ref_vals[val_idx]; + + len = trace_stack(entry, event, stack, + data_size, &n_u64); + data_size += len; } else { struct synth_field *field = event->fields[i]; u64 val = var_ref_vals[val_idx]; @@ -572,6 +644,9 @@ static int __set_synth_event_print_fmt(struct synth_event *event, event->fields[i]->is_dynamic) pos += snprintf(buf + pos, LEN_OR_ZERO, ", __get_str(%s)", event->fields[i]->name); + else if (event->fields[i]->is_stack) + pos += snprintf(buf + pos, LEN_OR_ZERO, + ", __get_stacktrace(%s)", event->fields[i]->name); else pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s", event->fields[i]->name); @@ -708,7 +783,8 @@ static struct synth_field *parse_synth_field(int argc, char **argv, ret = -EINVAL; goto free; } else if (size == 0) { - if (synth_field_is_string(field->type)) { + if (synth_field_is_string(field->type) || + synth_field_is_stack(field->type)) { char *type;
len = sizeof("__data_loc ") + strlen(field->type) + 1; @@ -739,6 +815,8 @@ static struct synth_field *parse_synth_field(int argc, char **argv,
if (synth_field_is_string(field->type)) field->is_string = true; + else if (synth_field_is_stack(field->type)) + field->is_stack = true;
field->is_signed = synth_field_signed(field->type); out: diff --git a/kernel/trace/trace_synth.h b/kernel/trace/trace_synth.h index b29595fe3ac5a..43f6fb6078dbf 100644 --- a/kernel/trace/trace_synth.h +++ b/kernel/trace/trace_synth.h @@ -18,6 +18,7 @@ struct synth_field { bool is_signed; bool is_string; bool is_dynamic; + bool is_stack; };
struct synth_event {