user/sven/linux.git/include/linux/perf_event.h, branch v6.1.13

perf: Fix missing SIGTRAPs

2022-10-17T14:32:05Z

Marco reported: Due to the implementation of how SIGTRAP are delivered if perf_event_attr::sigtrap is set, we've noticed 3 issues: 1. Missing SIGTRAP due to a race with event_sched_out() (more details below). 2. Hardware PMU events being disabled due to returning 1 from perf_event_overflow(). The only way to re-enable the event is for user space to first "properly" disable the event and then re-enable it. 3. The inability to automatically disable an event after a specified number of overflows via PERF_EVENT_IOC_REFRESH. The worst of the 3 issues is problem (1), which occurs when a pending_disable is "consumed" by a racing event_sched_out(), observed as follows: CPU0 | CPU1 --------------------------------+--------------------------- __perf_event_overflow() | perf_event_disable_inatomic() | pending_disable = CPU0 | ... | _perf_event_enable() | event_function_call() | task_function_call() | /* sends IPI to CPU0 */ | ... __perf_event_enable() +--------------------------- ctx_resched() task_ctx_sched_out() ctx_sched_out() group_sched_out() event_sched_out() pending_disable = -1 perf_pending_event() perf_pending_event_disable() /* Fails to send SIGTRAP because no pending_disable! */ In the above case, not only is that particular SIGTRAP missed, but also all future SIGTRAPs because 'event_limit' is not reset back to 1. To fix, rework pending delivery of SIGTRAP via IRQ-work by introduction of a separate 'pending_sigtrap', no longer using 'event_limit' and 'pending_disable' for its delivery. Additionally; and different to Marco's proposed patch: - recognise that pending_disable effectively duplicates oncpu for the case where it is set. As such, change the irq_work handler to use ->oncpu to target the event and use pending_* as boolean toggles. - observe that SIGTRAP targets the ctx->task, so the context switch optimization that carries contexts between tasks is invalid. If the irq_work were delayed enough to hit after a context switch the SIGTRAP would be delivered to the wrong task. - observe that if the event gets scheduled out (rotation/migration/context-switch/...) the irq-work would be insufficient to deliver the SIGTRAP when the event gets scheduled back in (the irq-work might still be pending on the old CPU). Therefore have event_sched_out() convert the pending sigtrap into a task_work which will deliver the signal at return_to_user. Fixes: 97ba62b27867 ("perf: Add support for SIGTRAP on perf events") Reported-by: Dmitry Vyukov Debugged-by: Dmitry Vyukov Reported-by: Marco Elver Debugged-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Marco Elver Tested-by: Marco Elver

perf: Fix lockdep_assert_event_ctx()

2022-10-04T11:32:08Z

I'm a flamin' moron; because even after Mark told me it should be '&&' I still got it wrong in the final commit. Fixes: f3c0eba28704 ("perf: Add a few assertions") Reported-by: Borislav Petkov Reported-by: Mark Rutland Signed-off-by: Peter Zijlstra (Intel) Tested-by: Borislav Petkov Link: https://lkml.kernel.org/r/YvvIWmDBWdIUCMZj@FVFF77S0Q05N

perf: Use sample_flags for raw_data

2022-09-27T20:50:24Z

Use the new sample_flags to indicate whether the raw data field is filled by the PMU driver. Although it could check with the NULL, follow the same rule with other fields. Remove the raw field from the perf_sample_data_init() to minimize the number of cache lines touched. Signed-off-by: Namhyung Kim Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20220921220032.2858517-2-namhyung@kernel.org

perf: Use sample_flags for addr

2022-09-27T20:50:24Z

Use the new sample_flags to indicate whether the addr field is filled by the PMU driver. As most PMU drivers pass 0, it can set the flag only if it has a non-zero value. And use 0 in perf_sample_output() if it's not filled already. Signed-off-by: Namhyung Kim Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20220921220032.2858517-1-namhyung@kernel.org

perf: Add a few assertions

2022-09-07T19:54:01Z

While auditing 6b959ba22d34 ("perf/core: Fix reentry problem in perf_output_read_group()") a few spots were found that wanted assertions. Notable for_each_sibling_event() relies on exclusion from modification. This would normally be holding either ctx->lock or ctx->mutex, however due to how things are constructed disabling IRQs is a valid and sufficient substitute for ctx->lock. Another possible site to add assertions would be the various pmu::{add,del,read,..}() methods, but that's not trivially expressable in C -- the best option is wrappers, but those are easy enough to forget. Signed-off-by: Peter Zijlstra (Intel)

perf/core: Assert PERF_EVENT_FLAG_ARCH does not overlap with generic flags

2022-09-07T19:54:00Z

This just ensures that PERF_EVENT_FLAG_ARCH does not overlap with generic hardware event flags. Signed-off-by: Anshuman Khandual Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: James Clark Link: https://lkml.kernel.org/r/20220907091924.439193-3-anshuman.khandual@arm.com

perf/core: Expand PERF_EVENT_FLAG_ARCH

2022-09-07T19:54:00Z

Two hardware event flags on x86 platform has overshot PERF_EVENT_FLAG_ARCH (0x0000ffff). These flags are PERF_X86_EVENT_PEBS_LAT_HYBRID (0x20000) and PERF_X86_EVENT_AMD_BRS (0x10000). Lets expand PERF_EVENT_FLAG_ARCH mask to accommodate those flags, and also create room for two more in the future. Signed-off-by: Anshuman Khandual Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: James Clark Link: https://lkml.kernel.org/r/20220907091924.439193-2-anshuman.khandual@arm.com

perf: Consolidate branch sample filter helpers

2022-09-07T19:54:00Z

Besides the branch type filtering requests, 'event.attr.branch_sample_type' also contains various flags indicating which additional information should be captured, along with the base branch record. These flags help configure the underlying hardware, and capture the branch records appropriately when required e.g after PMU interrupt. But first, this moves an existing helper perf_sample_save_hw_index() into the header before adding some more helpers for other branch sample filter flags. Signed-off-by: Anshuman Khandual Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20220906084414.396220-1-anshuman.khandual@arm.com

perf: Use sample_flags for txn

2022-09-06T09:33:03Z

Use the new sample_flags to indicate whether the txn field is filled by the PMU driver. Remove the txn field from the perf_sample_data_init() to minimize the number of cache lines touched. Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20220901130959.1285717-7-kan.liang@linux.intel.com

perf: Use sample_flags for data_src

2022-09-06T09:33:03Z

Use the new sample_flags to indicate whether the data_src field is filled by the PMU driver. Remove the data_src field from the perf_sample_data_init() to minimize the number of cache lines touched. Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20220901130959.1285717-6-kan.liang@linux.intel.com