From nobody Sun Feb 8 11:16:27 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 A0BA024502F; Tue, 8 Apr 2025 19:05:04 +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=1744139107; cv=none; b=Sk6DpSM2qRFUSHivmvj8LaYdYEPrCZFRu49zyVj3Z7j05DJwp75+tigF2mjhxMIi8fOPWBJET+wXC6SQ5TYb1+CoHGsrLH8yoNhBIR/xReG/Ort+8QtFJg+8TcBV9asa2aC+bHSxe9d4IQMLOF0kywyxCpgSpwv8k2ag/FlwCLc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744139107; c=relaxed/simple; bh=f/NH6PG4B1U/uU5au6qSRRJfGFNzBa5v0Frfnm1KSn8=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=tF8JU90eOXQzd1yjH0zdSEPQCkHpvlwPAlLnYB1RBNAMR41pzfxq1r07hGkqGIy08RIEW+6Nz3zKq5nIDSLAtRPTCW1inx08Jnq+VvvqixoCPwf/p2b1waArges7CxyIq9MW4UsIKX0Yi823qDBNr0Bug2ZqW+IQuhm6Y/NWyzA= 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=UXQWE/wZ; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=iFXGwAVg; 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="UXQWE/wZ"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="iFXGwAVg" Date: Tue, 08 Apr 2025 19:05:02 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1744139103; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=a2yRtr0lcbuWsQky97Dcqb8VM2ncby/AQb0WIeXAHaE=; b=UXQWE/wZ/o+H4IRk+FxDKJ/IDTHFlYhEmdT+gfQ/rVHDs1egs55ACaFyfVFRwkzFPuJdYL gP8Du4gFPEbu6WriYSyCYR9yoScd/Gv5lEitSV5u0XSWrIM57e0iXAsw+5RuWchzhOQlLL ANmORycmn1WgtgkJpZYOBpRPhZY9mMjR02tWK+U69twYdMfqvZrrp13Z2ns9Cmwi1YtRU2 tQ6QL7vYFiy0HwWOcVpxdyG0jfqiCFwTn8s+qWGVGcwT+hePIQlj13NgtnNBrkgqc8l04g jihgBh/rkTUYarnYDbBlBzkImqeM38ATmEvS6/f31+VB2ukViREa7eMB+WxN6w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1744139103; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=a2yRtr0lcbuWsQky97Dcqb8VM2ncby/AQb0WIeXAHaE=; b=iFXGwAVggRrcfV6DYW/tBXztmSwQ8NYgO0JTOmxPHUWSv8mKGWNr47JVgXZ16Fpw+6rDak 6F3ohWc9mT/7bbCw== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: perf/core] perf: Unify perf_event_free_task() / perf_event_exit_task_context() Cc: "Peter Zijlstra (Intel)" , Ravi Bangoria , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250307193723.274039710@infradead.org> References: <20250307193723.274039710@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <174413910259.31282.6563263873790654487.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the perf/core branch of tip: Commit-ID: 90661365021a6d0d7f3a2c5046ebe33e4df53b92 Gitweb: https://git.kernel.org/tip/90661365021a6d0d7f3a2c5046ebe33e4= df53b92 Author: Peter Zijlstra AuthorDate: Thu, 13 Feb 2025 14:04:07 +01:00 Committer: Peter Zijlstra CommitterDate: Tue, 08 Apr 2025 20:55:47 +02:00 perf: Unify perf_event_free_task() / perf_event_exit_task_context() Both perf_event_free_task() and perf_event_exit_task_context() are very similar, except perf_event_exit_task_context() is a little more generic / makes less assumptions. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Ravi Bangoria Link: https://lkml.kernel.org/r/20250307193723.274039710@infradead.org --- kernel/events/core.c | 93 +++++++++++-------------------------------- 1 file changed, 25 insertions(+), 68 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index f75b0d3..85c8b79 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -13742,13 +13742,11 @@ perf_event_exit_event(struct perf_event *event, s= truct perf_event_context *ctx) perf_event_wakeup(event); } =20 -static void perf_event_exit_task_context(struct task_struct *child) +static void perf_event_exit_task_context(struct task_struct *child, bool e= xit) { struct perf_event_context *child_ctx, *clone_ctx =3D NULL; struct perf_event *child_event, *next; =20 - WARN_ON_ONCE(child !=3D current); - child_ctx =3D perf_pin_task_context(child); if (!child_ctx) return; @@ -13771,7 +13769,8 @@ static void perf_event_exit_task_context(struct tas= k_struct *child) * in. */ raw_spin_lock_irq(&child_ctx->lock); - task_ctx_sched_out(child_ctx, NULL, EVENT_ALL); + if (exit) + task_ctx_sched_out(child_ctx, NULL, EVENT_ALL); =20 /* * Now that the context is inactive, destroy the task <-> ctx relation @@ -13780,7 +13779,7 @@ static void perf_event_exit_task_context(struct tas= k_struct *child) RCU_INIT_POINTER(child->perf_event_ctxp, NULL); put_ctx(child_ctx); /* cannot be last */ WRITE_ONCE(child_ctx->task, TASK_TOMBSTONE); - put_task_struct(current); /* cannot be last */ + put_task_struct(child); /* cannot be last */ =20 clone_ctx =3D unclone_ctx(child_ctx); raw_spin_unlock_irq(&child_ctx->lock); @@ -13793,13 +13792,31 @@ static void perf_event_exit_task_context(struct t= ask_struct *child) * won't get any samples after PERF_RECORD_EXIT. We can however still * get a few PERF_RECORD_READ events. */ - perf_event_task(child, child_ctx, 0); + if (exit) + perf_event_task(child, child_ctx, 0); =20 list_for_each_entry_safe(child_event, next, &child_ctx->event_list, event= _entry) perf_event_exit_event(child_event, child_ctx); =20 mutex_unlock(&child_ctx->mutex); =20 + if (!exit) { + /* + * perf_event_release_kernel() could still have a reference on + * this context. In that case we must wait for these events to + * have been freed (in particular all their references to this + * task must've been dropped). + * + * Without this copy_process() will unconditionally free this + * task (irrespective of its reference count) and + * _free_event()'s put_task_struct(event->hw.target) will be a + * use-after-free. + * + * Wait for all events to drop their context reference. + */ + wait_var_event(&child_ctx->refcount, + refcount_read(&child_ctx->refcount) =3D=3D 1); + } put_ctx(child_ctx); } =20 @@ -13827,7 +13844,7 @@ void perf_event_exit_task(struct task_struct *child) } mutex_unlock(&child->perf_event_mutex); =20 - perf_event_exit_task_context(child); + perf_event_exit_task_context(child, true); =20 /* * The perf_event_exit_task_context calls perf_event_task @@ -13844,25 +13861,6 @@ void perf_event_exit_task(struct task_struct *chil= d) detach_task_ctx_data(child); } =20 -static void perf_free_event(struct perf_event *event, - struct perf_event_context *ctx) -{ - struct perf_event *parent =3D event->parent; - - if (WARN_ON_ONCE(!parent)) - return; - - mutex_lock(&parent->child_mutex); - list_del_init(&event->child_list); - mutex_unlock(&parent->child_mutex); - - raw_spin_lock_irq(&ctx->lock); - perf_group_detach(event); - list_del_event(event, ctx); - raw_spin_unlock_irq(&ctx->lock); - put_event(event); -} - /* * Free a context as created by inheritance by perf_event_init_task() belo= w, * used by fork() in case of fail. @@ -13872,48 +13870,7 @@ static void perf_free_event(struct perf_event *eve= nt, */ void perf_event_free_task(struct task_struct *task) { - struct perf_event_context *ctx; - struct perf_event *event, *tmp; - - ctx =3D rcu_access_pointer(task->perf_event_ctxp); - if (!ctx) - return; - - mutex_lock(&ctx->mutex); - raw_spin_lock_irq(&ctx->lock); - /* - * Destroy the task <-> ctx relation and mark the context dead. - * - * This is important because even though the task hasn't been - * exposed yet the context has been (through child_list). - */ - RCU_INIT_POINTER(task->perf_event_ctxp, NULL); - WRITE_ONCE(ctx->task, TASK_TOMBSTONE); - put_task_struct(task); /* cannot be last */ - raw_spin_unlock_irq(&ctx->lock); - - - list_for_each_entry_safe(event, tmp, &ctx->event_list, event_entry) - perf_free_event(event, ctx); - - mutex_unlock(&ctx->mutex); - - /* - * perf_event_release_kernel() could've stolen some of our - * child events and still have them on its free_list. In that - * case we must wait for these events to have been freed (in - * particular all their references to this task must've been - * dropped). - * - * Without this copy_process() will unconditionally free this - * task (irrespective of its reference count) and - * _free_event()'s put_task_struct(event->hw.target) will be a - * use-after-free. - * - * Wait for all events to drop their context reference. - */ - wait_var_event(&ctx->refcount, refcount_read(&ctx->refcount) =3D=3D 1); - put_ctx(ctx); /* must be last */ + perf_event_exit_task_context(task, false); } =20 void perf_event_delayed_put(struct task_struct *task)