bpf: Replace cant_sleep() with cant_migrate()

As already discussed in the previous change which introduced
BPF_RUN_PROG_PIN_ON_CPU() BPF only requires to disable migration to
guarantee per CPUness.

If RT substitutes the preempt disable based migration protection then the
cant_sleep() check will obviously trigger as preemption is not disabled.

Replace it by cant_migrate() which maps to cant_sleep() on a non RT kernel
and will verify that migration is disabled on a full RT kernel.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200224145643.583038889@linutronix.de

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 38f60188bb26e8e83ebd0f24f1dc06b5f22c34a6..1982a52eb4c9e1b63bcf01934f069fadb1d18bd0 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -561,7 +561,7 @@ DECLARE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
 
 #define __BPF_PROG_RUN(prog, ctx, dfunc)       ({                      \
        u32 ret;                                                        \
-       cant_sleep();                                                   \
+       cant_migrate();                                                 \
        if (static_branch_unlikely(&bpf_stats_enabled_key)) {           \
                struct bpf_prog_stats *stats;                           \
                u64 start = sched_clock();                              \