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If sbi_ecall.c's functions are traceable, echo "__sbi_ecall:snapshot" > /sys/kernel/tracing/set_ftrace_filter may get the kernel into a deadlock. (Functions in sbi_ecall.c are excluded from tracing if CONFIG_RISCV_ALTERNATIVE_EARLY is set.) __sbi_ecall triggers a snapshot of the ringbuffer. The snapshot code raises an IPI interrupt, which results in another call to __sbi_ecall and another snapshot... All it takes to get into this endless loop is one initial __sbi_ecall. On RISC-V systems without SSTC extension, the clock events in timer-riscv.c issue periodic sbi ecalls, making the problem easy to trigger. Always exclude the sbi_ecall.c functions from tracing to fix the potential deadlock. sbi ecalls can easiliy be logged via trace events, excluding ecall functions from function tracing is not a big limitation. Signed-off-by: Martin Kaiser <martin@kaiser.cx> Link: https://patch.msgid.link/20251223135043.1336524-1-martin@kaiser.cx Signed-off-by: Paul Walmsley <pjw@kernel.org>