From nobody Mon Feb 9 19:05:39 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 D9DF340861; Fri, 8 Mar 2024 17:58:21 +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=1709920703; cv=none; b=uTVpdh5gEF1APwVVge1sRzomCXnul3QFUv8oNn793Y2c4DkxSm5wgEaU2hIZs7WO5dGdn2aQUNbomoT+drOd9FLu+70olJSOkAEVK5KxqDSDFL4RLCw+CmBwCsQVrYk0r9Zrtg+HTY0QRCQwRrcSok5qr6ulwIgsW/obmWCu3dE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709920703; c=relaxed/simple; bh=qgIOhCi1AT5/KkPlVlTKGgFIpu/HZ3VsmyhH2xLz0Ws=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MktAfAZmXFfXDYAYlwYAjba3Q4Bql7MHtp69yrkGKkluXc+D2RMP9VcU5SI2VgfGkW1OTzanB+DZJPegAwg3NtdJelS/UDL00ZC9lL2JX6SnhRLEbhsW3IEmsfHqBG5wp8jK4Bo8fbX8WP+dVHMV0kjcV3En61MBa1EZuBj4TCA= 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=JV4ty8dQ; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=YJBdep7/; 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="JV4ty8dQ"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="YJBdep7/" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1709920700; 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=xk1CSY2j/Du8Z3nH9cehrGYPSezPuuWTJQyDu/5RHlc=; b=JV4ty8dQlJElZcsroYiiZ914/yQt/Yer5CzQbRo9i2nuCjUCqZ64EIAXcOo+ox0ut4x/bd rosSSDROA4j4m4SxQRXWMAq2wt44UmwVtcV2SuAb0gKGdCXdmLnRXv8FHl6+3AeJIp4ePY 2/YTljWk1UeNjPA1EdSVVJBU7EnSVxJ3MMbxjU6Om4PbKtTmKwMWwFBUrrMNKsx4alkuRm lek+kHr3+GcT9BFQpFoqn/y5eRNmOoMDcCu9KtSHuKr5e8bGLbsUF/t0N+zD6NNGJ3oWgQ aTNe54hxf7ApwH85TYXY3bYI1Kgcdl7/aG4JpY9ncUkUxIVPLNcII9hKzXGnzg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1709920700; 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=xk1CSY2j/Du8Z3nH9cehrGYPSezPuuWTJQyDu/5RHlc=; b=YJBdep7/6jVdWfH49/GIFla8t1NJkLGvNkRNgK3L5DM5IGlxgxVukz6HUXU/ORoOHf+BoX zgAuKav8usy12mDg== 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 , Mark Rutland , Namhyung Kim , Peter Zijlstra , Thomas Gleixner , Sebastian Andrzej Siewior Subject: [PATCH 2/4] perf: Enqueue SIGTRAP always via task_work. Date: Fri, 8 Mar 2024 18:51:28 +0100 Message-ID: <20240308175810.2894694-3-bigeasy@linutronix.de> In-Reply-To: <20240308175810.2894694-1-bigeasy@linutronix.de> References: <20240308175810.2894694-1-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" 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 instead triggering irq_work. Queue signal via task_work. Remove perf_event::pending_sigtrap and and use perf_event::pending_work instead. Signed-off-by: Sebastian Andrzej Siewior --- include/linux/perf_event.h | 3 +-- kernel/events/core.c | 31 ++++++------------------------- 2 files changed, 7 insertions(+), 27 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index d2a15c0c6f8a9..24ac6765146c7 100644 --- 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; @@ -959,7 +958,7 @@ struct perf_event_context { struct rcu_head rcu_head; =20 /* - * 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. diff --git a/kernel/events/core.c b/kernel/events/core.c index c7a0274c662c8..e4a85d6d2d685 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2283,21 +2283,6 @@ event_sched_out(struct perf_event *event, struct per= f_event_context *ctx) state =3D PERF_EVENT_STATE_OFF; } =20 - if (event->pending_sigtrap) { - bool dec =3D true; - - event->pending_sigtrap =3D 0; - if (state !=3D PERF_EVENT_STATE_OFF && - !event->pending_work) { - event->pending_work =3D 1; - dec =3D false; - WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); - task_work_add(current, &event->pending_task, TWA_RESUME); - } - if (dec) - local_dec(&event->ctx->nr_pending); - } - perf_event_set_state(event, state); =20 if (!is_software_event(event)) @@ -6741,11 +6726,6 @@ static void __perf_pending_irq(struct perf_event *ev= ent) * Yay, we hit home and are in the context of the event. */ if (cpu =3D=3D smp_processor_id()) { - if (event->pending_sigtrap) { - event->pending_sigtrap =3D 0; - perf_sigtrap(event); - local_dec(&event->ctx->nr_pending); - } if (event->pending_disable) { event->pending_disable =3D 0; perf_event_disable_local(event); @@ -9592,14 +9572,15 @@ static int __perf_event_overflow(struct perf_event = *event, =20 if (regs) pending_id =3D hash32_ptr((void *)instruction_pointer(regs)) ?: 1; - if (!event->pending_sigtrap) { - event->pending_sigtrap =3D pending_id; + if (!event->pending_work) { + event->pending_work =3D pending_id; local_inc(&event->ctx->nr_pending); - irq_work_queue(&event->pending_irq); + WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount)); + task_work_add(current, &event->pending_task, TWA_RESUME); } 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. @@ -9609,7 +9590,7 @@ static int __perf_event_overflow(struct perf_event *e= vent, * To approximate progress (with false negatives), * check 32-bit hash of the current IP. */ - WARN_ON_ONCE(event->pending_sigtrap !=3D pending_id); + WARN_ON_ONCE(event->pending_work !=3D pending_id); } =20 event->pending_addr =3D 0; --=20 2.43.0