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sched/tracing: Append prev_state to tp args instead

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Commit fa2c3254d7 (sched/tracing: Don't re-read p->state when emitting
sched_switch event, 2022-01-20) added a new prev_state argument to the
sched_switch tracepoint, before the prev task_struct pointer.

This reordering of arguments broke BPF programs that use the raw
tracepoint (e.g. tp_btf programs). The type of the second argument has
changed and existing programs that assume a task_struct* argument
(e.g. for bpf_task_storage access) will now fail to verify.

If we instead append the new argument to the end, all existing programs
would continue to work and can conditionally extract the prev_state
argument on supported kernel versions.

Fixes: fa2c3254d7 (sched/tracing: Don't re-read p->state when emitting sched_switch event, 2022-01-20)
Signed-off-by: Delyan Kratunov <delyank@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com
This commit is contained in:
Delyan Kratunov
2022-05-11 18:28:36 +00:00
committed by Peter Zijlstra
parent c5eb0a6123
commit 9c2136be08
9 changed files with 21 additions and 21 deletions
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6
include/trace/events/sched.h
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@@ -222,11 +222,11 @@ static inline long __trace_sched_switch_state(bool preempt,
TRACE_EVENT(sched_switch,
TP_PROTO(bool preempt,
unsigned int prev_state,
struct task_struct *prev,
struct task_struct *next),
struct task_struct *next,
unsigned int prev_state),
TP_ARGS(preempt, prev_state, prev, next),
TP_ARGS(preempt, prev, next, prev_state),
TP_STRUCT__entry(
__array( char, prev_comm, TASK_COMM_LEN )