From 46538818023e8ea94f656acfa1e38297e2df20e2 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 12 Sep 2009 02:43:45 +0200 Subject: perf sched: Fix bad event alignment perf sched raises the following error when it meets a sched switch event: perf: builtin-sched.c:286: register_pid: Assertion `!(pid >= 65536)' failed. Abandon Currently in x86-64, the sched switch events have a hole in the middle of the structure: u16 common_type; u8 common_flags; u8 common_preempt_count; u32 common_pid; u32 common_tgid; char prev_comm[16]; u32 prev_pid; u32 prev_prio; <--- there u64 prev_state; char next_comm[16]; u32 next_pid; u32 next_prio; Gcc inserts a 4 bytes hole there for prev_state to be u64 aligned. And the events are exported to userspace with this hole. But in userspace, from perf sched, we fetch it using a structure that has a new field in the beginning: u32 size. This is because our trace is exported with its size as a field. But now that we have this new field, the hole in the middle disappears because it makes prev_state becoming well aligned. And since we are using a pointer to the raw trace using this struct, instead of reading prev_state, we are reading the hole. We could fix it by keeping the size seperate from the struct but actually there a lot of other potential problems: some fields may be saved as long in a 64 bits system and later read as long in a 32 bits system. Also this direct cast doesn't care about the endianness differences between the host traced machine and the machine in which we do the post processing. So instead of using such dangerous direct casts, fetch the values using the trace parsing API that already takes care of all these problems. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Signed-off-by: Ingo Molnar --- tools/perf/util/trace-event.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'tools/perf/util/trace-event.h') diff --git a/tools/perf/util/trace-event.h b/tools/perf/util/trace-event.h index bc81612fd24..d35ebf1e29f 100644 --- a/tools/perf/util/trace-event.h +++ b/tools/perf/util/trace-event.h @@ -236,6 +236,9 @@ extern int header_page_data_size; int parse_header_page(char *buf, unsigned long size); int trace_parse_common_type(void *data); struct event *trace_find_event(int id); +unsigned long long +raw_field_value(struct event *event, const char *name, void *data); +void *raw_field_ptr(struct event *event, const char *name, void *data); void read_tracing_data(struct perf_counter_attr *pattrs, int nb_counters); -- cgit v1.2.2