* [PATCH 1/2] tracing/wakeup: Balance prolog on fgraph failure
@ 2025-10-06 17:58 Sasha Levin
2025-10-06 17:58 ` [PATCH 2/2] tracing/irqsoff: " Sasha Levin
2025-10-08 15:24 ` [PATCH 1/2] tracing/wakeup: " Steven Rostedt
0 siblings, 2 replies; 4+ messages in thread
From: Sasha Levin @ 2025-10-06 17:58 UTC (permalink / raw)
To: rostedt, mhiramat
Cc: mathieu.desnoyers, linux-kernel, linux-trace-kernel, Sasha Levin
Commit a485ea9e3ef3 ("tracing: Fix irqsoff and wakeup latency tracers when
using function graph") added fgraph_reserve_data()/fgraph_retrieve_data() to
the wakeup tracer's function-graph hooks.
When func_prolog_preempt_disable() succeeded but those calls failed, the code
returned without undoing the prolog (no local_dec(&data->disabled), no
preempt_enable_notrace()). That leaked a preempt disable into later code and
could trigger "BUG: scheduling while atomic".
Balance the prolog on these failure paths in both entry and return hooks.
Fixes: a485ea9e3ef3 ("tracing: Fix irqsoff and wakeup latency tracers when using function graph")
Assisted-by: gpt-5-codex
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/trace/trace_sched_wakeup.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index bf1cb80742aed..fa48bbdf0851c 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -138,8 +138,11 @@ static int wakeup_graph_entry(struct ftrace_graph_ent *trace,
return 0;
calltime = fgraph_reserve_data(gops->idx, sizeof(*calltime));
- if (!calltime)
+ if (!calltime) {
+ local_dec(&data->disabled);
+ preempt_enable_notrace();
return 0;
+ }
*calltime = trace_clock_local();
@@ -169,8 +172,11 @@ static void wakeup_graph_return(struct ftrace_graph_ret *trace,
rettime = trace_clock_local();
calltime = fgraph_retrieve_data(gops->idx, &size);
- if (!calltime)
+ if (!calltime) {
+ local_dec(&data->disabled);
+ preempt_enable_notrace();
return;
+ }
__trace_graph_return(tr, trace, trace_ctx, *calltime, rettime);
local_dec(&data->disabled);
--
2.51.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH 2/2] tracing/irqsoff: Balance prolog on fgraph failure 2025-10-06 17:58 [PATCH 1/2] tracing/wakeup: Balance prolog on fgraph failure Sasha Levin @ 2025-10-06 17:58 ` Sasha Levin 2025-10-08 15:27 ` Steven Rostedt 2025-10-08 15:24 ` [PATCH 1/2] tracing/wakeup: " Steven Rostedt 1 sibling, 1 reply; 4+ messages in thread From: Sasha Levin @ 2025-10-06 17:58 UTC (permalink / raw) To: rostedt, mhiramat Cc: mathieu.desnoyers, linux-kernel, linux-trace-kernel, Sasha Levin Commit a485ea9e3ef3 ("tracing: Fix irqsoff and wakeup latency tracers when using function graph") added fgraph_reserve_data()/fgraph_retrieve_data() to the irqsoff tracer's function-graph hooks. When func_prolog_dec() succeeded but those calls failed, the code returned without undoing the prolog (no local_dec(&data->disabled)). While func_prolog_dec() does not disable preemption, this left the tracer recursion guard (data->disabled) incremented on this CPU, suppressing subsequent tracing and leaving the tracer state inconsistent. Balance the prolog on these failure paths in both entry and return hooks. Fixes: a485ea9e3ef3 ("tracing: Fix irqsoff and wakeup latency tracers when using function graph") Assisted-by: gpt-5-codex Signed-off-by: Sasha Levin <sashal@kernel.org> --- kernel/trace/trace_irqsoff.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c index 5496758b6c760..39152ef3d2432 100644 --- a/kernel/trace/trace_irqsoff.c +++ b/kernel/trace/trace_irqsoff.c @@ -202,8 +202,10 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace, return 0; calltime = fgraph_reserve_data(gops->idx, sizeof(*calltime)); - if (!calltime) + if (!calltime) { + local_dec(&data->disabled); return 0; + } *calltime = trace_clock_local(); @@ -233,8 +235,10 @@ static void irqsoff_graph_return(struct ftrace_graph_ret *trace, rettime = trace_clock_local(); calltime = fgraph_retrieve_data(gops->idx, &size); - if (!calltime) + if (!calltime) { + local_dec(&data->disabled); return; + } trace_ctx = tracing_gen_ctx_flags(flags); __trace_graph_return(tr, trace, trace_ctx, *calltime, rettime); -- 2.51.0 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 2/2] tracing/irqsoff: Balance prolog on fgraph failure 2025-10-06 17:58 ` [PATCH 2/2] tracing/irqsoff: " Sasha Levin @ 2025-10-08 15:27 ` Steven Rostedt 0 siblings, 0 replies; 4+ messages in thread From: Steven Rostedt @ 2025-10-08 15:27 UTC (permalink / raw) To: Sasha Levin; +Cc: mhiramat, mathieu.desnoyers, linux-kernel, linux-trace-kernel On Mon, 6 Oct 2025 13:58:48 -0400 Sasha Levin <sashal@kernel.org> wrote: > diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c > index 5496758b6c760..39152ef3d2432 100644 > --- a/kernel/trace/trace_irqsoff.c > +++ b/kernel/trace/trace_irqsoff.c > @@ -202,8 +202,10 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace, > return 0; > > calltime = fgraph_reserve_data(gops->idx, sizeof(*calltime)); > - if (!calltime) > + if (!calltime) { > + local_dec(&data->disabled); > return 0; > + } > > *calltime = trace_clock_local(); > > @@ -233,8 +235,10 @@ static void irqsoff_graph_return(struct ftrace_graph_ret *trace, > > rettime = trace_clock_local(); > calltime = fgraph_retrieve_data(gops->idx, &size); > - if (!calltime) > + if (!calltime) { > + local_dec(&data->disabled); > return; > + } > > trace_ctx = tracing_gen_ctx_flags(flags); > __trace_graph_return(tr, trace, trace_ctx, *calltime, rettime); > -- Technically correct, but this would look better: diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c index 5496758b6c76..4c45c49b06c8 100644 --- a/kernel/trace/trace_irqsoff.c +++ b/kernel/trace/trace_irqsoff.c @@ -184,7 +184,7 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace, unsigned long flags; unsigned int trace_ctx; u64 *calltime; - int ret; + int ret = 0; if (ftrace_graph_ignore_func(gops, trace)) return 0; @@ -202,13 +202,11 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace, return 0; calltime = fgraph_reserve_data(gops->idx, sizeof(*calltime)); - if (!calltime) - return 0; - - *calltime = trace_clock_local(); - - trace_ctx = tracing_gen_ctx_flags(flags); - ret = __trace_graph_entry(tr, trace, trace_ctx); + if (calltime) { + *calltime = trace_clock_local(); + trace_ctx = tracing_gen_ctx_flags(flags); + ret = __trace_graph_entry(tr, trace, trace_ctx); + } local_dec(&data->disabled); return ret; @@ -233,11 +231,10 @@ static void irqsoff_graph_return(struct ftrace_graph_ret *trace, rettime = trace_clock_local(); calltime = fgraph_retrieve_data(gops->idx, &size); - if (!calltime) - return; - - trace_ctx = tracing_gen_ctx_flags(flags); - __trace_graph_return(tr, trace, trace_ctx, *calltime, rettime); + if (calltime) { + trace_ctx = tracing_gen_ctx_flags(flags); + __trace_graph_return(tr, trace, trace_ctx, *calltime, rettime); + } local_dec(&data->disabled); } -- Steve ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 1/2] tracing/wakeup: Balance prolog on fgraph failure 2025-10-06 17:58 [PATCH 1/2] tracing/wakeup: Balance prolog on fgraph failure Sasha Levin 2025-10-06 17:58 ` [PATCH 2/2] tracing/irqsoff: " Sasha Levin @ 2025-10-08 15:24 ` Steven Rostedt 1 sibling, 0 replies; 4+ messages in thread From: Steven Rostedt @ 2025-10-08 15:24 UTC (permalink / raw) To: Sasha Levin; +Cc: mhiramat, mathieu.desnoyers, linux-kernel, linux-trace-kernel On Mon, 6 Oct 2025 13:58:47 -0400 Sasha Levin <sashal@kernel.org> wrote: > diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c > index bf1cb80742aed..fa48bbdf0851c 100644 > --- a/kernel/trace/trace_sched_wakeup.c > +++ b/kernel/trace/trace_sched_wakeup.c > @@ -138,8 +138,11 @@ static int wakeup_graph_entry(struct ftrace_graph_ent *trace, > return 0; > > calltime = fgraph_reserve_data(gops->idx, sizeof(*calltime)); > - if (!calltime) > + if (!calltime) { > + local_dec(&data->disabled); > + preempt_enable_notrace(); > return 0; > + } > > *calltime = trace_clock_local(); > > @@ -169,8 +172,11 @@ static void wakeup_graph_return(struct ftrace_graph_ret *trace, > rettime = trace_clock_local(); > > calltime = fgraph_retrieve_data(gops->idx, &size); > - if (!calltime) > + if (!calltime) { > + local_dec(&data->disabled); > + preempt_enable_notrace(); > return; > + } > > __trace_graph_return(tr, trace, trace_ctx, *calltime, rettime); > local_dec(&data->disabled); Technically correct, but this would look better: diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c index bf1cb80742ae..e3f2e4f56faa 100644 --- a/kernel/trace/trace_sched_wakeup.c +++ b/kernel/trace/trace_sched_wakeup.c @@ -138,12 +138,10 @@ static int wakeup_graph_entry(struct ftrace_graph_ent *trace, return 0; calltime = fgraph_reserve_data(gops->idx, sizeof(*calltime)); - if (!calltime) - return 0; - - *calltime = trace_clock_local(); - - ret = __trace_graph_entry(tr, trace, trace_ctx); + if (calltime) { + *calltime = trace_clock_local(); + ret = __trace_graph_entry(tr, trace, trace_ctx); + } local_dec(&data->disabled); preempt_enable_notrace(); @@ -169,12 +167,10 @@ static void wakeup_graph_return(struct ftrace_graph_ret *trace, rettime = trace_clock_local(); calltime = fgraph_retrieve_data(gops->idx, &size); - if (!calltime) - return; + if (calltime) + __trace_graph_return(tr, trace, trace_ctx, *calltime, rettime); - __trace_graph_return(tr, trace, trace_ctx, *calltime, rettime); local_dec(&data->disabled); - preempt_enable_notrace(); return; } -- Steve ^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2025-10-08 15:25 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2025-10-06 17:58 [PATCH 1/2] tracing/wakeup: Balance prolog on fgraph failure Sasha Levin 2025-10-06 17:58 ` [PATCH 2/2] tracing/irqsoff: " Sasha Levin 2025-10-08 15:27 ` Steven Rostedt 2025-10-08 15:24 ` [PATCH 1/2] tracing/wakeup: " Steven Rostedt
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