From patchwork Thu Oct 24 14:55:49 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13849332 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 27CBC1E25FC; Thu, 24 Oct 2024 15:04:26 +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=1729782268; cv=none; b=o/XyC/5mTh0Vte/KF9nh1u8PGL8ZQaYo7hsnsguNsDRaeAZsPlA/wk7mHce7mvZrIyHOLxAjg/OskXSUncHskSDbENa7+OtJBIGfJiJ9CvSKuS4p40paMRvVkP6TAHJH3y1hHOdyN+cdFZ9A2Xd2XbUD9ob7Lfl9X7tOTZf7CbU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729782268; c=relaxed/simple; bh=HfyR1ZRYXkjKZkd7RtAB0OlErMa6eGDmJY5BJT+005Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FJVyU7kS824hZR/2GUNeeJIBOAuXTkXwNemFrBtgm83HC461q2X+lzbSSIQ2u+5J+4zyxpDR3AI8AU94yR+ZYswQXlOA4UqNjVXJRSzxpbI7WiAd2gMhvk0u1XVg9aXmfRFTIHDhi9ITkVkelE+VFTeUc3ffmvK1nmnPaXnLP2E= 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=tLooQmms; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=Xtl84M/d; 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="tLooQmms"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Xtl84M/d" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1729782259; 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=6RBUgezimWTlIVj/xJQsYpKXFWuoCJnPRQ023lCFpxc=; b=tLooQmms20Ua0zXdO9iXeUIMbV7lqwOT3v8CnHfoOZzCEmzRgFJiB8N7gewtRQCipT55Hb mZPVyqsOBYU7aS3wgFmQh/tuhG9EjUgk7WVlScq5mI+uzgxEAo36sHMIAgvQlEotjfBg1N F4cCs1Pw+Of7k846sepSFDUl/8OjaOid2i9o60SZQRtTvO2A8mCcChLBWN1mJaDet5AJPN Y7bHJE6tiDCurxgM81TvtKWA6xL3d5RaLIpWkcQEBuTahExbbf4+O2JE0YtpbOSnIlUD2f o+I9Z/41icIdVUXiBKGzjmtaR75I36zMoB0YcS+TgUIcg0DD00l7NMSM+MN6RQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1729782259; 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=6RBUgezimWTlIVj/xJQsYpKXFWuoCJnPRQ023lCFpxc=; b=Xtl84M/de/F+xuJqjvUBmsxBchv5CDrGRv3Pz84UsRez/up2PCawXOQEGIOp8wRkmhea49 ++W/RG7OJItg8hAQ== To: linux-kernel@vger.kernel.org, rcu@vger.kernel.org Cc: "Paul E. McKenney" , Anna-Maria Behnsen , Davidlohr Bueso , Frederic Weisbecker , Ingo Molnar , Josh Triplett , Thomas Gleixner , Sebastian Andrzej Siewior Subject: [PATCH v2 1/3] hrtimer: Use __raise_softirq_irqoff() to raise the softirq. Date: Thu, 24 Oct 2024 16:55:49 +0200 Message-ID: <20241024150413.518862-2-bigeasy@linutronix.de> In-Reply-To: <20241024150413.518862-1-bigeasy@linutronix.de> References: <20241024150413.518862-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 As an optimisation use __raise_softirq_irqoff() to raise the softirq. This is always called from an interrupt handler so it can be reduced to just or set softirq flag and let softirq be invoked on return from interrupt. Use __raise_softirq_irqoff() to raise the softirq. Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Frederic Weisbecker --- kernel/time/hrtimer.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index cddcd08ea827f..5402e0f242178 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1811,7 +1811,7 @@ void hrtimer_interrupt(struct clock_event_device *dev) if (!ktime_before(now, cpu_base->softirq_expires_next)) { cpu_base->softirq_expires_next = KTIME_MAX; cpu_base->softirq_activated = 1; - raise_softirq_irqoff(HRTIMER_SOFTIRQ); + __raise_softirq_irqoff(HRTIMER_SOFTIRQ); } __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD); @@ -1906,7 +1906,7 @@ void hrtimer_run_queues(void) if (!ktime_before(now, cpu_base->softirq_expires_next)) { cpu_base->softirq_expires_next = KTIME_MAX; cpu_base->softirq_activated = 1; - raise_softirq_irqoff(HRTIMER_SOFTIRQ); + __raise_softirq_irqoff(HRTIMER_SOFTIRQ); } __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD); From patchwork Thu Oct 24 14:55:50 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13849333 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 27D2A1E2614; Thu, 24 Oct 2024 15:04:26 +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=1729782269; cv=none; b=XvkWYhtGxrEbTZr5bxE2EPUzMzO7tPp2BI/xsh3aqUuVrVj4Ev2ci1Kdxs2pjlcwzQXjXmLNQsHRYqd8dCF8AH1vURM0TPOjx7uI7QyIqRwY3NRLQZvNsOxp6W5q3sxvVHCQh/ef2uTLbu81d3oHgQGBu1rP8zHvNxxIK0D5Bhs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729782269; c=relaxed/simple; bh=/7ZRVvFwZ+7VQnjOzyeKR08bCh1EnmmIHVHoSnjt+ko=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pWESrfqpbpKfGFOyQrKXi07RzwcK14/CGjWvIkn8+MaeLePiQotblHAeKKHBRVZ75dzy81yAeuXdiOOy+WQsRfZXCFgKfmsVXuL+pF3g3TAGEAUr4lOKKiM8W8N/HLr4vrV2mVkv5Oi1r++ghwcUyF9oGu3eZXV4pmOkrqZt1TE= 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=zPV6ARtp; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=5KxvyAXc; 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="zPV6ARtp"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="5KxvyAXc" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1729782260; 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=xnZElyqVxUkhY65aKgaxFCt3b1HrfEQgNljIzazjk7c=; b=zPV6ARtpY3ZsdtxuWmZkox2fm8QWFRR7BGRAvOsMh5QgA6HX8X2UCQuUKNw8XmGrtfiiNr jDUrYp+aHh+XGLrC/OnWzHJxqbQddWQg3QsBlJ9MJAk4Hnr5a5DokqMwWx7FCDdu2MwKQo XjiDLK7P540SEtm/pztQjhcCxIWmvKBTOpOz6gz/e+7rFSy2+melBxE2XFoOeXpQrVMsBm MrDkRthxnxLZ04qDOZ7Z0upEhdVj7zkVMUpXL/u/BiwacPRwQbItihPdJ+f9IAiqD2HiJI 2jxax3Jz48Bxtiz3zuxpNjolfGGfiYple2XezfJ8n4zJLdGUXWtsBM+6zj25zg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1729782260; 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=xnZElyqVxUkhY65aKgaxFCt3b1HrfEQgNljIzazjk7c=; b=5KxvyAXcr3/r/erHSX5No2gYMnsPSKcb+YWtn6pkqzBzE08M8Cek8xGyRGtqfddVz0CG7L 2+IpHZ5pz4dlIODQ== To: linux-kernel@vger.kernel.org, rcu@vger.kernel.org Cc: "Paul E. McKenney" , Anna-Maria Behnsen , Davidlohr Bueso , Frederic Weisbecker , Ingo Molnar , Josh Triplett , Thomas Gleixner , Sebastian Andrzej Siewior Subject: [PATCH v2 2/3] timers: Use __raise_softirq_irqoff() to raise the softirq. Date: Thu, 24 Oct 2024 16:55:50 +0200 Message-ID: <20241024150413.518862-3-bigeasy@linutronix.de> In-Reply-To: <20241024150413.518862-1-bigeasy@linutronix.de> References: <20241024150413.518862-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 As an optimisation use __raise_softirq_irqoff() to raise the softirq. This is always called from an interrupt handler, interrupts are already disabled so it can be reduced to just or set softirq flag and let softirq be invoked on return from interrupt. Use __raise_softirq_irqoff() to raise the softirq. Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Frederic Weisbecker --- kernel/time/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 0fc9d066a7be4..1759de934284c 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -2499,7 +2499,7 @@ static void run_local_timers(void) */ if (time_after_eq(jiffies, READ_ONCE(base->next_expiry)) || (i == BASE_DEF && tmigr_requires_handle_remote())) { - raise_softirq(TIMER_SOFTIRQ); + __raise_softirq_irqoff(TIMER_SOFTIRQ); return; } } From patchwork Thu Oct 24 14:55:51 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13849334 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 27D7D1E377D; Thu, 24 Oct 2024 15:04:26 +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=1729782269; cv=none; b=fHiQYxKiCQF7gyhKSeC4iFX2hqJa2YgiLy/GjyLEYXoxQGbe9bntxtQ1fxdIaQRrh+GzgIecGyxhGFV/M66aQnoeORIGhknlW6ELByFN+Oq/bgV62WxhAISfWncAV8suoCCNFl0/aVxEeSxUC7BMlkYuJRQUfV3oBiA20DyRJ8w= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729782269; c=relaxed/simple; bh=xcGhakrZUBn48OepV138/F7Fax1Vq6RyEkJQAX6vOCA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=phpE+S772E59wjBMqazFLTKyE/3qZzMAigKyneConV6hJrg0pZjTrWaQwtxXQkejyY9lwycpvnLoyzIl1T2S0XByRIBH31Sibfoago6hh5wqqf8JYPv8CnCVOk00geurz0coJYKMJIE427CCDDmhL4+ayN6o58y5bGTrqQSvYoc= 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=GVzKZVHv; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=9iwJxl1a; 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="GVzKZVHv"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="9iwJxl1a" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1729782260; 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=N/12p1wmUAGKBLrwHiGde7XNj74xQnBZYdchqQ0uIiA=; b=GVzKZVHvTWU/hEVDPA4LpwKsGqciuLzfyLhE7NmxRj9ieJAijHXp0MFrLigvA1QtW9s3Lm bnoCaZ17u02ZRjRGJGs9hZYfhMtbopvvN4J/SDvbTZeHcxik8ZrEwidad6zS8+oQhzq7Xg WG5dOoUNd+5joW9WZl57V7K4o9YkqoGMrMcXNzbv+ZM6rSbNCFwDh8OSZHVRoIyYjj+zQZ JXa1ot7KAaWpSxp2nZE9syjGyQggMwL11jjA2APB2Q7ixHh5qYX9mpES+moZAFYoB5V8nw LLckmlSj51HFfLPWi1eqrgKzwmFkCNqCXNPAnlunFzd6PTDkR9WqyGhy1cdaJg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1729782260; 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=N/12p1wmUAGKBLrwHiGde7XNj74xQnBZYdchqQ0uIiA=; b=9iwJxl1aau/1a/3xsGIkftUvETeuDro6EWvPDsM3gh0Na8RWbKKFjVyI48boBhpHqWXGtR /GWA1bmcdK7et4Dw== To: linux-kernel@vger.kernel.org, rcu@vger.kernel.org Cc: "Paul E. McKenney" , Anna-Maria Behnsen , Davidlohr Bueso , Frederic Weisbecker , Ingo Molnar , Josh Triplett , Thomas Gleixner , Sebastian Andrzej Siewior Subject: [PATCH v2 3/3] softirq: Use a dedicated thread for timer wakeups on PREEMPT_RT. Date: Thu, 24 Oct 2024 16:55:51 +0200 Message-ID: <20241024150413.518862-4-bigeasy@linutronix.de> In-Reply-To: <20241024150413.518862-1-bigeasy@linutronix.de> References: <20241024150413.518862-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 A timer/ hrtimer softirq is raised in-IRQ context. With threaded interrupts enabled or on PREEMPT_RT this leads to waking the ksoftirqd for the processing of the softirq. ksoftirqd runs as SCHED_OTHER which means it will compete with other tasks for CPU ressources. This can introduce long delays for timer processing on heavy loaded systems and is not desired. Split the TIMER_SOFTIRQ and HRTIMER_SOFTIRQ processing into a dedicated timers thread and let it run at the lowest SCHED_FIFO priority. Wake-ups for RT tasks happen from hardirq context so only timer_list timers and hrtimers for "regular" tasks are processed here. The higher priority ensures that wakeups are performed before scheduling SCHED_OTHER tasks. Using a dedicated variable to store the pending softirq bits values ensure that the timer are not accidentally picked up by ksoftirqd and other threaded interrupts. It shouldn't be picked up by ksoftirqd since it runs at lower priority. However if ksoftirqd is already running while a timer fires, then ksoftird will be PI-boosted due to the BH-lock to ktimer's priority. Ideally we try to avoid having ksoftirqd running. The timer thread can pick up pending softirqs from ksoftirqd but only if the softirq load is high. It is not be desired that the picked up softirqs are processed at SCHED_FIFO priority under high softirq load but this can already happen by a PI-boost by a force-threaded interrupt. [ frederic@kernel.org: rcutorture.c fixes, storm fix by introduction of local_timers_pending() for tick_nohz_next_event() ] [ junxiao.chang@intel.com: Ensure ktimersd gets woken up even if a softirq is currently served. ] Reviewed-by: Paul E. McKenney [rcutorture] Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Frederic Weisbecker --- include/linux/interrupt.h | 44 +++++++++++++++++++++++++ kernel/rcu/rcutorture.c | 6 ++++ kernel/softirq.c | 69 ++++++++++++++++++++++++++++++++++++++- kernel/time/hrtimer.c | 4 +-- kernel/time/tick-sched.c | 2 +- kernel/time/timer.c | 2 +- 6 files changed, 122 insertions(+), 5 deletions(-) diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index 457151f9f263d..9637af78087f3 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -616,6 +616,50 @@ extern void __raise_softirq_irqoff(unsigned int nr); extern void raise_softirq_irqoff(unsigned int nr); extern void raise_softirq(unsigned int nr); +/* + * Handle timers in a dedicated thread at a low SCHED_FIFO priority instead in + * ksoftirqd as to be prefred over SCHED_NORMAL tasks. + */ +#ifdef CONFIG_PREEMPT_RT +DECLARE_PER_CPU(struct task_struct *, timersd); +DECLARE_PER_CPU(unsigned long, pending_timer_softirq); + +void raise_ktimers_thread(unsigned int nr); + +static inline void raise_timer_softirq(void) +{ + raise_ktimers_thread(TIMER_SOFTIRQ); +} + +static inline void raise_hrtimer_softirq(void) +{ + raise_ktimers_thread(HRTIMER_SOFTIRQ); +} + +static inline unsigned int local_timers_pending(void) +{ + return __this_cpu_read(pending_timer_softirq); +} + +#else +static inline void raise_timer_softirq(void) +{ + lockdep_assert_in_irq(); + __raise_softirq_irqoff(TIMER_SOFTIRQ); +} + +static inline void raise_hrtimer_softirq(void) +{ + lockdep_assert_in_irq(); + __raise_softirq_irqoff(HRTIMER_SOFTIRQ); +} + +static inline unsigned int local_timers_pending(void) +{ + return local_softirq_pending(); +} +#endif + DECLARE_PER_CPU(struct task_struct *, ksoftirqd); static inline struct task_struct *this_cpu_ksoftirqd(void) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index bb75dbf5c800c..609687fd742d5 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -2440,6 +2440,12 @@ static int rcutorture_booster_init(unsigned int cpu) WARN_ON_ONCE(!t); sp.sched_priority = 2; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); +#ifdef CONFIG_PREEMPT_RT + t = per_cpu(timersd, cpu); + WARN_ON_ONCE(!t); + sp.sched_priority = 2; + sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); +#endif } /* Don't allow time recalculation while creating a new task. */ diff --git a/kernel/softirq.c b/kernel/softirq.c index d082e7840f880..b452206cf93b2 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -624,6 +624,24 @@ static inline void tick_irq_exit(void) #endif } +#ifdef CONFIG_PREEMPT_RT +DEFINE_PER_CPU(struct task_struct *, timersd); +DEFINE_PER_CPU(unsigned long, pending_timer_softirq); + +static void wake_timersd(void) +{ + struct task_struct *tsk = __this_cpu_read(timersd); + + if (tsk) + wake_up_process(tsk); +} + +#else + +static inline void wake_timersd(void) { } + +#endif + static inline void __irq_exit_rcu(void) { #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED @@ -636,6 +654,10 @@ static inline void __irq_exit_rcu(void) if (!in_interrupt() && local_softirq_pending()) invoke_softirq(); + if (IS_ENABLED(CONFIG_PREEMPT_RT) && local_timers_pending() && + !(in_nmi() | in_hardirq())) + wake_timersd(); + tick_irq_exit(); } @@ -971,12 +993,57 @@ static struct smp_hotplug_thread softirq_threads = { .thread_comm = "ksoftirqd/%u", }; +#ifdef CONFIG_PREEMPT_RT +static void timersd_setup(unsigned int cpu) +{ + /* Above SCHED_NORMAL to handle timers before regular tasks. */ + sched_set_fifo_low(current); +} + +static int timersd_should_run(unsigned int cpu) +{ + return local_timers_pending(); +} + +void raise_ktimers_thread(unsigned int nr) +{ + lockdep_assert_in_irq(); + trace_softirq_raise(nr); + __this_cpu_or(pending_timer_softirq, 1 << nr); +} + +static void run_timersd(unsigned int cpu) +{ + unsigned int timer_si; + + ksoftirqd_run_begin(); + + timer_si = local_timers_pending(); + __this_cpu_write(pending_timer_softirq, 0); + or_softirq_pending(timer_si); + + __do_softirq(); + + ksoftirqd_run_end(); +} + +static struct smp_hotplug_thread timer_threads = { + .store = &timersd, + .setup = timersd_setup, + .thread_should_run = timersd_should_run, + .thread_fn = run_timersd, + .thread_comm = "ktimers/%u", +}; +#endif + static __init int spawn_ksoftirqd(void) { cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL, takeover_tasklets); BUG_ON(smpboot_register_percpu_thread(&softirq_threads)); - +#ifdef CONFIG_PREEMPT_RT + BUG_ON(smpboot_register_percpu_thread(&timer_threads)); +#endif return 0; } early_initcall(spawn_ksoftirqd); diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 5402e0f242178..133d49f703d93 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1811,7 +1811,7 @@ void hrtimer_interrupt(struct clock_event_device *dev) if (!ktime_before(now, cpu_base->softirq_expires_next)) { cpu_base->softirq_expires_next = KTIME_MAX; cpu_base->softirq_activated = 1; - __raise_softirq_irqoff(HRTIMER_SOFTIRQ); + raise_hrtimer_softirq(); } __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD); @@ -1906,7 +1906,7 @@ void hrtimer_run_queues(void) if (!ktime_before(now, cpu_base->softirq_expires_next)) { cpu_base->softirq_expires_next = KTIME_MAX; cpu_base->softirq_activated = 1; - __raise_softirq_irqoff(HRTIMER_SOFTIRQ); + raise_hrtimer_softirq(); } __hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD); diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 753a184c70907..976a212cca2e8 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -859,7 +859,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) static inline bool local_timer_softirq_pending(void) { - return local_softirq_pending() & BIT(TIMER_SOFTIRQ); + return local_timers_pending() & BIT(TIMER_SOFTIRQ); } /* diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 1759de934284c..79f0dc73ac436 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -2499,7 +2499,7 @@ static void run_local_timers(void) */ if (time_after_eq(jiffies, READ_ONCE(base->next_expiry)) || (i == BASE_DEF && tmigr_requires_handle_remote())) { - __raise_softirq_irqoff(TIMER_SOFTIRQ); + raise_timer_softirq(); return; } }