From: "Steven Rostedt (VMware)" <rost...@goodmis.org> To make it easier for ftrace callbacks to have recursion protection, provide a ftrace_test_recursion_trylock() and ftrace_test_recursion_unlock() helper that tests for recursion.
Link: https://lkml.kernel.org/r/20201028115612.634927...@goodmis.org Link: https://lkml.kernel.org/r/20201106023546.378584...@goodmis.org Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> --- include/linux/trace_recursion.h | 25 +++++++++++++++++++++++++ kernel/trace/trace_functions.c | 12 +++++------- 2 files changed, 30 insertions(+), 7 deletions(-) diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h index dbb7b6d4c94c..f2a949dbfec7 100644 --- a/include/linux/trace_recursion.h +++ b/include/linux/trace_recursion.h @@ -183,5 +183,30 @@ static __always_inline void trace_clear_recursion(int bit) current->trace_recursion = val; } +/** + * ftrace_test_recursion_trylock - tests for recursion in same context + * + * Use this for ftrace callbacks. This will detect if the function + * tracing recursed in the same context (normal vs interrupt), + * + * Returns: -1 if a recursion happened. + * >= 0 if no recursion + */ +static __always_inline int ftrace_test_recursion_trylock(void) +{ + return trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX); +} + +/** + * ftrace_test_recursion_unlock - called when function callback is complete + * @bit: The return of a successful ftrace_test_recursion_trylock() + * + * This is used at the end of a ftrace callback. + */ +static __always_inline void ftrace_test_recursion_unlock(int bit) +{ + trace_clear_recursion(bit); +} + #endif /* CONFIG_TRACING */ #endif /* _LINUX_TRACE_RECURSION_H */ diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index 2c2126e1871d..943756c01190 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -141,22 +141,20 @@ function_trace_call(unsigned long ip, unsigned long parent_ip, if (unlikely(!tr->function_enabled)) return; + bit = ftrace_test_recursion_trylock(); + if (bit < 0) + return; + pc = preempt_count(); preempt_disable_notrace(); - bit = trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX); - if (bit < 0) - goto out; - cpu = smp_processor_id(); data = per_cpu_ptr(tr->array_buffer.data, cpu); if (!atomic_read(&data->disabled)) { local_save_flags(flags); trace_function(tr, ip, parent_ip, flags, pc); } - trace_clear_recursion(bit); - - out: + ftrace_test_recursion_unlock(bit); preempt_enable_notrace(); } -- 2.28.0
