diff options
Diffstat (limited to 'debian/patches-rt/0003-perf-Enqueue-SIGTRAP-always-via-task_work.patch')
| -rw-r--r-- | debian/patches-rt/0003-perf-Enqueue-SIGTRAP-always-via-task_work.patch | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/debian/patches-rt/0003-perf-Enqueue-SIGTRAP-always-via-task_work.patch b/debian/patches-rt/0003-perf-Enqueue-SIGTRAP-always-via-task_work.patch new file mode 100644 index 0000000000..725fb82046 --- /dev/null +++ b/debian/patches-rt/0003-perf-Enqueue-SIGTRAP-always-via-task_work.patch @@ -0,0 +1,120 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Thu, 4 Jul 2024 19:03:37 +0200 +Subject: [PATCH 3/7] perf: Enqueue SIGTRAP always via task_work. +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz + +A signal is delivered by raising irq_work() which works from any context +including NMI. irq_work() can be delayed if the architecture does not +provide an interrupt vector. In order not to lose a signal, the signal +is injected via task_work during event_sched_out(). + +Instead going via irq_work, the signal could be added directly via +task_work. The signal is sent to current and can be enqueued on its +return path to userland. + +Queue signal via task_work and consider possible NMI context. Remove +perf_event::pending_sigtrap and and use perf_event::pending_work +instead. + +Tested-by: Marco Elver <elver@google.com> +Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> +Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com> +Link: https://lore.kernel.org/all/ZMAtZ2t43GXoF6tM@kernel.org/ +Link: https://lore.kernel.org/r/20240704170424.1466941-4-bigeasy@linutronix.de +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/perf_event.h | 3 +-- + kernel/events/core.c | 31 ++++++++++--------------------- + 2 files changed, 11 insertions(+), 23 deletions(-) + +--- a/include/linux/perf_event.h ++++ b/include/linux/perf_event.h +@@ -781,7 +781,6 @@ struct perf_event { + unsigned int pending_wakeup; + unsigned int pending_kill; + unsigned int pending_disable; +- unsigned int pending_sigtrap; + unsigned long pending_addr; /* SIGTRAP */ + struct irq_work pending_irq; + struct callback_head pending_task; +@@ -963,7 +962,7 @@ struct perf_event_context { + struct rcu_head rcu_head; + + /* +- * Sum (event->pending_sigtrap + event->pending_work) ++ * Sum (event->pending_work + event->pending_work) + * + * The SIGTRAP is targeted at ctx->task, as such it won't do changing + * that until the signal is delivered. +--- a/kernel/events/core.c ++++ b/kernel/events/core.c +@@ -2283,17 +2283,6 @@ event_sched_out(struct perf_event *event + state = PERF_EVENT_STATE_OFF; + } + +- if (event->pending_sigtrap) { +- event->pending_sigtrap = 0; +- if (state != PERF_EVENT_STATE_OFF && +- !event->pending_work && +- !task_work_add(current, &event->pending_task, TWA_RESUME)) { +- event->pending_work = 1; +- } else { +- local_dec(&event->ctx->nr_pending); +- } +- } +- + perf_event_set_state(event, state); + + if (!is_software_event(event)) +@@ -6787,11 +6776,6 @@ static void __perf_pending_irq(struct pe + * Yay, we hit home and are in the context of the event. + */ + if (cpu == smp_processor_id()) { +- if (event->pending_sigtrap) { +- event->pending_sigtrap = 0; +- perf_sigtrap(event); +- local_dec(&event->ctx->nr_pending); +- } + if (event->pending_disable) { + event->pending_disable = 0; + perf_event_disable_local(event); +@@ -9732,21 +9716,26 @@ static int __perf_event_overflow(struct + */ + bool valid_sample = sample_is_allowed(event, regs); + unsigned int pending_id = 1; ++ enum task_work_notify_mode notify_mode; + + if (regs) + pending_id = hash32_ptr((void *)instruction_pointer(regs)) ?: 1; +- if (!event->pending_sigtrap) { +- event->pending_sigtrap = pending_id; ++ ++ notify_mode = in_nmi() ? TWA_NMI_CURRENT : TWA_RESUME; ++ ++ if (!event->pending_work && ++ !task_work_add(current, &event->pending_task, notify_mode)) { ++ event->pending_work = pending_id; + local_inc(&event->ctx->nr_pending); + + event->pending_addr = 0; + if (valid_sample && (data->sample_flags & PERF_SAMPLE_ADDR)) + event->pending_addr = data->addr; +- irq_work_queue(&event->pending_irq); ++ + } else if (event->attr.exclude_kernel && valid_sample) { + /* + * Should not be able to return to user space without +- * consuming pending_sigtrap; with exceptions: ++ * consuming pending_work; with exceptions: + * + * 1. Where !exclude_kernel, events can overflow again + * in the kernel without returning to user space. +@@ -9756,7 +9745,7 @@ static int __perf_event_overflow(struct + * To approximate progress (with false negatives), + * check 32-bit hash of the current IP. + */ +- WARN_ON_ONCE(event->pending_sigtrap != pending_id); ++ WARN_ON_ONCE(event->pending_work != pending_id); + } + } + |