From d33cc657372366a8959f099c619a208b4c5dc664 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E7=8E=8B=E8=B4=87?= Date: Wed, 27 Oct 2021 11:15:11 +0800 Subject: ftrace: do CPU checking after preemption disabled With CONFIG_DEBUG_PREEMPT we observed reports like: BUG: using smp_processor_id() in preemptible caller is perf_ftrace_function_call+0x6f/0x2e0 CPU: 1 PID: 680 Comm: a.out Not tainted Call Trace: dump_stack_lvl+0x8d/0xcf check_preemption_disabled+0x104/0x110 ? optimize_nops.isra.7+0x230/0x230 ? text_poke_bp_batch+0x9f/0x310 perf_ftrace_function_call+0x6f/0x2e0 ... __text_poke+0x5/0x620 text_poke_bp_batch+0x9f/0x310 This telling us the CPU could be changed after task is preempted, and the checking on CPU before preemption will be invalid. Since now ftrace_test_recursion_trylock() will help to disable the preemption, this patch just do the checking after trylock() to address the issue. Link: https://lkml.kernel.org/r/54880691-5fe2-33e7-d12f-1fa6136f5183@linux.alibaba.com CC: Steven Rostedt Cc: Guo Ren Cc: Ingo Molnar Cc: "James E.J. Bottomley" Cc: Helge Deller Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Albert Ou Cc: Thomas Gleixner Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: Josh Poimboeuf Cc: Jiri Kosina Cc: Miroslav Benes Cc: Petr Mladek Cc: Joe Lawrence Cc: Masami Hiramatsu Cc: "Peter Zijlstra (Intel)" Cc: Nicholas Piggin Cc: Jisheng Zhang Reported-by: Abaci Signed-off-by: Michael Wang Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_event_perf.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel/trace/trace_event_perf.c') diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index 6aed10e2f7ce..fba8cb77a73a 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -441,13 +441,13 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, if (!rcu_is_watching()) return; - if ((unsigned long)ops->private != smp_processor_id()) - return; - bit = ftrace_test_recursion_trylock(ip, parent_ip); if (bit < 0) return; + if ((unsigned long)ops->private != smp_processor_id()) + goto out; + event = container_of(ops, struct perf_event, ftrace_ops); /* -- cgit v1.2.3 From a90afe8d020da9298c98fddb19b7a6372e2feb45 Mon Sep 17 00:00:00 2001 From: "Robin H. Johnson" Date: Mon, 30 Aug 2021 21:37:22 -0700 Subject: tracing: Show size of requested perf buffer If the perf buffer isn't large enough, provide a hint about how large it needs to be for whatever is running. Link: https://lkml.kernel.org/r/20210831043723.13481-1-robbat2@gentoo.org Signed-off-by: Robin H. Johnson Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_event_perf.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/trace/trace_event_perf.c') diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index fba8cb77a73a..a114549720d6 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -400,7 +400,8 @@ void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp) BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, - "perf buffer not large enough")) + "perf buffer not large enough, wanted %d, have %d", + size, PERF_MAX_TRACE_SIZE)) return NULL; *rctxp = rctx = perf_swevent_get_recursion_context(); -- cgit v1.2.3