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0f0c332992
Allowing sleepable programs to use tail calls. Making sure we can't mix sleepable and non-sleepable bpf programs in tail call map (BPF_MAP_TYPE_PROG_ARRAY) and allowing it to be used in sleepable programs. Sleepable programs can be preempted and sleep which might bring new source of race conditions, but both direct and indirect tail calls should not be affected. Direct tail calls work by patching direct jump to callee into bpf caller program, so no problem there. We atomically switch from nop to jump instruction. Indirect tail call reads the callee from the map and then jumps to it. The callee bpf program can't disappear (be released) from the caller, because it is executed under rcu lock (rcu_read_lock_trace). Signed-off-by: Jiri Olsa <jolsa@kernel.org> Acked-by: Leon Hwang <leon.hwang@linux.dev> Link: https://lore.kernel.org/r/20260130081208.1130204-2-jolsa@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>