On 1/8/25 14:34, Sebastian Andrzej Siewior wrote:
__module_text_address() can be invoked within a RCU section, there is no requirement to have preemption disabled. Replace the preempt_disable() section around __module_text_address() with RCU. Cc: Christophe Leroy <[email protected]> Cc: Madhavan Srinivasan <[email protected]> Cc: Mark Rutland <[email protected]> Cc: Masami Hiramatsu <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: Naveen N Rao <[email protected]> Cc: Nicholas Piggin <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: [email protected] Cc: [email protected] Acked-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- arch/powerpc/kernel/trace/ftrace.c | 6 ++---- arch/powerpc/kernel/trace/ftrace_64_pg.c | 6 ++---- 2 files changed, 4 insertions(+), 8 deletions(-)
Ran ftrace (function graph) on preempt=full kernel with rcutorture while doing modprobe/rmmod. rcutorture succeeded and didn't see any splats. If there is any other method to test it out, please let me know. So for powerpc bits: Tested-by: Shrikanth Hegde <[email protected]>
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c index 5ccd791761e8f..558d7f4e4bea6 100644 --- a/arch/powerpc/kernel/trace/ftrace.c +++ b/arch/powerpc/kernel/trace/ftrace.c @@ -115,10 +115,8 @@ static unsigned long ftrace_lookup_module_stub(unsigned long ip, unsigned long a { struct module *mod = NULL;- preempt_disable();- mod = __module_text_address(ip); - preempt_enable(); - + scoped_guard(rcu) + mod = __module_text_address(ip); if (!mod) pr_err("No module loaded at addr=%lx\n", ip);diff --git a/arch/powerpc/kernel/trace/ftrace_64_pg.c b/arch/powerpc/kernel/trace/ftrace_64_pg.cindex 98787376eb87c..531d40f10c8a1 100644 --- a/arch/powerpc/kernel/trace/ftrace_64_pg.c +++ b/arch/powerpc/kernel/trace/ftrace_64_pg.c @@ -120,10 +120,8 @@ static struct module *ftrace_lookup_module(struct dyn_ftrace *rec) { struct module *mod;- preempt_disable();- mod = __module_text_address(rec->ip); - preempt_enable(); - + scoped_guard(rcu) + mod = __module_text_address(rec->ip); if (!mod) pr_err("No module loaded at addr=%lx\n", rec->ip);
