From nobody Tue Feb 10 05:26:37 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8E63E1386D8; Tue, 12 Mar 2024 18:08:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710266904; cv=none; b=cmAIpQtBqm6fJOBuTut095owvQ8TZOPBedS7v+dccR4R2F6/vfUGTHtoCa2D00kIf6oLt4FcKZv5znwUZsu2wVzhHju9nJeM8/zdjlM25V0DwWL5ijsLoz1ZMsMAQ+pdUw5Xsyb1h/y2A5f2MvEajCaev4i2BlcBUBDAiLvmxJ8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710266904; c=relaxed/simple; bh=c3RmwsE63wrR9rwinoDk/iQsOuyG4zNU5E4UVMKVuGg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UcfFbxg+l0rOvFZwODgphcvixvDWjJE8lLUHws3yQAWDiKn3MPD2ytORS2+f7hcMtvHEyOjEfzMM4d1G7LU+/ozHf+CWIE56Mm7Is1biUeBvY1U03+2VMrh4Culxl/vV8/fFSsMdQr/vRe1fv08qLG5U1GK9Vy06GxNYbhDp/PM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=pvCNqIBc; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=+7e0kFLc; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="pvCNqIBc"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="+7e0kFLc" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1710266900; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=s85+LWr3GUAFugfSGnQlcG4gV/dvTGj/TQOXg49YnL8=; b=pvCNqIBc2IjnnFRffOrX62nWsq0MOzO/4UkxBxjqqbWtyrdTvMKUt4G+epjDV9e0yBamg6 FmWEcwgr1L6xuivlS7hH4zXrRgNiX2KfVdbZFUOOp1cxFtEDea8AMyXN0A6GEojyNT4Mwu Ho39bhLuDfHO/0uLMN1iJIP828Z0sHaxsKjAu4KC05XEH8TVhlBfPrwNJJqtzRaTohZcm7 2teDDSD+6DQFPnP2AH1EpodRnKT3brMGAdIChJi74jhTF/TBMZzmz509wLJhGeGMUAqqpL q/E67n20SgIcTFRAeJNrBw6eYRTdfphNBXsKRdnweLR7WYwMNo/OqDZIBK89Wg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1710266900; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=s85+LWr3GUAFugfSGnQlcG4gV/dvTGj/TQOXg49YnL8=; b=+7e0kFLctOs/4SSNohdj4923xFKm3YSxEtkAbnpj3TDWyGChxSqxV7SuQ8caDkjzhpWd8x ezoIbSip4TBHbhCA== To: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Adrian Hunter , Alexander Shishkin , Arnaldo Carvalho de Melo , Ian Rogers , Ingo Molnar , Jiri Olsa , Marco Elver , Mark Rutland , Namhyung Kim , Peter Zijlstra , Thomas Gleixner , Sebastian Andrzej Siewior Subject: [PATCH v2 4/4] perf: Split __perf_pending_irq() out of perf_pending_irq() Date: Tue, 12 Mar 2024 19:01:52 +0100 Message-ID: <20240312180814.3373778-5-bigeasy@linutronix.de> In-Reply-To: <20240312180814.3373778-1-bigeasy@linutronix.de> References: <20240312180814.3373778-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" perf_pending_irq() invokes perf_event_wakeup() and __perf_pending_irq(). The former is in charge of waking any tasks which wait to be woken up while the latter disables perf-events. The irq_work perf_pending_irq(), while this an irq_work, the callback is invoked in thread context on PREEMPT_RT. This is needed because all the waking functions (wake_up_all(), kill_fasync()) acquire sleep locks which must not be used with disabled interrupts. Disabling events, as done by __perf_pending_irq(), expects a hardirq context and disabled interrupts. This requirement is not fulfilled on PREEMPT_RT. Split functionality based on perf_event::pending_disable into irq_work named `pending_disable_irq' and invoke it in hardirq context on PREEMPT_RT. Rename the split out callback to perf_pending_disable(). Signed-off-by: Sebastian Andrzej Siewior --- include/linux/perf_event.h | 1 + kernel/events/core.c | 31 +++++++++++++++++++++++-------- 2 files changed, 24 insertions(+), 8 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 24ac6765146c7..c1c6600541657 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -783,6 +783,7 @@ struct perf_event { unsigned int pending_disable; unsigned long pending_addr; /* SIGTRAP */ struct irq_work pending_irq; + struct irq_work pending_disable_irq; struct callback_head pending_task; unsigned int pending_work; =20 diff --git a/kernel/events/core.c b/kernel/events/core.c index 806514d76d8dc..9aafb949fa100 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2449,7 +2449,7 @@ static void __perf_event_disable(struct perf_event *e= vent, * hold the top-level event's child_mutex, so any descendant that * goes to exit will block in perf_event_exit_event(). * - * When called from perf_pending_irq it's OK because event->ctx + * When called from perf_pending_disable it's OK because event->ctx * is the current context on this CPU and preemption is disabled, * hence we can't get into perf_event_task_sched_out for this context. */ @@ -2489,7 +2489,7 @@ EXPORT_SYMBOL_GPL(perf_event_disable); void perf_event_disable_inatomic(struct perf_event *event) { event->pending_disable =3D 1; - irq_work_queue(&event->pending_irq); + irq_work_queue(&event->pending_disable_irq); } =20 #define MAX_INTERRUPTS (~0ULL) @@ -5175,6 +5175,7 @@ static void perf_addr_filters_splice(struct perf_even= t *event, static void _free_event(struct perf_event *event) { irq_work_sync(&event->pending_irq); + irq_work_sync(&event->pending_disable_irq); =20 unaccount_event(event); =20 @@ -6711,7 +6712,7 @@ static void perf_sigtrap(struct perf_event *event) /* * Deliver the pending work in-event-context or follow the context. */ -static void __perf_pending_irq(struct perf_event *event) +static void __perf_pending_disable(struct perf_event *event) { int cpu =3D READ_ONCE(event->oncpu); =20 @@ -6749,11 +6750,26 @@ static void __perf_pending_irq(struct perf_event *e= vent) * irq_work_queue(); // FAILS * * irq_work_run() - * perf_pending_irq() + * perf_pending_disable() * * But the event runs on CPU-B and wants disabling there. */ - irq_work_queue_on(&event->pending_irq, cpu); + irq_work_queue_on(&event->pending_disable_irq, cpu); +} + +static void perf_pending_disable(struct irq_work *entry) +{ + struct perf_event *event =3D container_of(entry, struct perf_event, pendi= ng_disable_irq); + int rctx; + + /* + * If we 'fail' here, that's OK, it means recursion is already disabled + * and we won't recurse 'further'. + */ + rctx =3D perf_swevent_get_recursion_context(); + __perf_pending_disable(event); + if (rctx >=3D 0) + perf_swevent_put_recursion_context(rctx); } =20 static void perf_pending_irq(struct irq_work *entry) @@ -6776,8 +6792,6 @@ static void perf_pending_irq(struct irq_work *entry) perf_event_wakeup(event); } =20 - __perf_pending_irq(event); - if (rctx >=3D 0) perf_swevent_put_recursion_context(rctx); } @@ -9566,7 +9580,7 @@ static int __perf_event_overflow(struct perf_event *e= vent, WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); task_work_add(current, &event->pending_task, TWA_RESUME); if (in_nmi()) - irq_work_queue(&event->pending_irq); + irq_work_queue(&event->pending_disable_irq); } else if (event->attr.exclude_kernel && valid_sample) { /* * Should not be able to return to user space without @@ -11906,6 +11920,7 @@ perf_event_alloc(struct perf_event_attr *attr, int = cpu, =20 init_waitqueue_head(&event->waitq); init_irq_work(&event->pending_irq, perf_pending_irq); + event->pending_disable_irq =3D IRQ_WORK_INIT_HARD(perf_pending_disable); init_task_work(&event->pending_task, perf_pending_task); =20 mutex_init(&event->mmap_mutex); --=20 2.43.0