From patchwork Wed Apr 20 14:16:57 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Ellerman X-Patchwork-Id: 1619583 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=pGaL3xj1; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org (client-ip=112.213.38.117; helo=lists.ozlabs.org; envelope-from=linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org; receiver=) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4Kk2n845ntz9sFq for ; Thu, 21 Apr 2022 00:17:31 +1000 (AEST) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Kk2n431W4z2ypD for ; Thu, 21 Apr 2022 00:17:28 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=pGaL3xj1; dkim-atps=neutral X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Received: from gandalf.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4Kk2mq4jxFz2yNF for ; Thu, 21 Apr 2022 00:17:15 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=pGaL3xj1; dkim-atps=neutral Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4Kk2mk2cXLz4xXj; Thu, 21 Apr 2022 00:17:10 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1650464230; bh=CRjmxCz6iBqvOPDZnQ7tgA2kXfn+x8a+axB6qW8tiCQ=; h=From:To:Cc:Subject:Date:From; b=pGaL3xj1WY0hE0xp5AOOlYNdTwaqkCstUwzFVs/2PLQPjRQmTVonpnuqbU1pe96ow VePeZmBQWPWMhmEuJ8ZebCBN99BY3J2DcDKE0P75uzd8AeSkTtlhiRrW8sIk6U0dZf /g03VusojcDxdR0kWoMRB5/PYA+lzvuHUaxIESmFGhBt+U9lORZN1Q1RrPg9euZ9qf BvipnB656RRtUKxaWei0sIWIoxnZ/YufPKpyzKLYfVgOwGq2fs0NFwnf5ottl36DUU bKR/8o2q8RflV8iM5nW6fZIMZ0/grnJJwNFkiZff9DifmYrP7psQSzTwoYYlYe8rWX O3YHyj8Fs1UVw== From: Michael Ellerman To: Subject: [PATCH] powerpc/time: Always set decrementer in timer_interrupt() Date: Thu, 21 Apr 2022 00:16:57 +1000 Message-Id: <20220420141657.771442-1-mpe@ellerman.id.au> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: miguel.ojeda.sandonis@gmail.com, npiggin@gmail.com Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" This is a partial revert of commit 0faf20a1ad16 ("powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless perf is in use"). Prior to that commit, we always set the decrementer in timer_interrupt(), to clear the timer interrupt. Otherwise we could end up continuously taking timer interrupts. When high res timers are enabled there is no problem seen with leaving the decrementer untouched in timer_interrupt(), because it will be programmed via hrtimer_interrupt() -> tick_program_event() -> clockevents_program_event() -> decrementer_set_next_event(). However with CONFIG_HIGH_RES_TIMERS=n or booting with highres=off, we see a stall/lockup, because tick_nohz_handler() does not cause a reprogram of the decrementer, leading to endless timer interrupts. Example trace: [ 1.898617][ T7] Freeing initrd memory: 2624K^M [ 22.680919][ C1] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:^M [ 22.682281][ C1] rcu: 0-....: (25 ticks this GP) idle=073/0/0x1 softirq=10/16 fqs=1050 ^M [ 22.682851][ C1] (detected by 1, t=2102 jiffies, g=-1179, q=476)^M [ 22.683649][ C1] Sending NMI from CPU 1 to CPUs 0:^M [ 22.685252][ C0] NMI backtrace for cpu 0^M [ 22.685649][ C0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.16.0-rc2-00185-g0faf20a1ad16 #145^M [ 22.686393][ C0] NIP: c000000000016d64 LR: c000000000f6cca4 CTR: c00000000019c6e0^M [ 22.686774][ C0] REGS: c000000002833590 TRAP: 0500 Not tainted (5.16.0-rc2-00185-g0faf20a1ad16)^M [ 22.687222][ C0] MSR: 8000000000009033 CR: 24000222 XER: 00000000^M [ 22.688297][ C0] CFAR: c00000000000c854 IRQMASK: 0 ^M ... [ 22.692637][ C0] NIP [c000000000016d64] arch_local_irq_restore+0x174/0x250^M [ 22.694443][ C0] LR [c000000000f6cca4] __do_softirq+0xe4/0x3dc^M [ 22.695762][ C0] Call Trace:^M [ 22.696050][ C0] [c000000002833830] [c000000000f6cc80] __do_softirq+0xc0/0x3dc (unreliable)^M [ 22.697377][ C0] [c000000002833920] [c000000000151508] __irq_exit_rcu+0xd8/0x130^M [ 22.698739][ C0] [c000000002833950] [c000000000151730] irq_exit+0x20/0x40^M [ 22.699938][ C0] [c000000002833970] [c000000000027f40] timer_interrupt+0x270/0x460^M [ 22.701119][ C0] [c0000000028339d0] [c0000000000099a8] decrementer_common_virt+0x208/0x210^M Possibly this should be fixed in the lowres timing code, but that would be a generic change and could take some time and may not backport easily, so for now make the programming of the decrementer unconditional again in timer_interrupt() to avoid the stall/lockup. Fixes: 0faf20a1ad16 ("powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless perf is in use") Reported-by: Miguel Ojeda Signed-off-by: Michael Ellerman Reviewed-by: Nicholas Piggin --- arch/powerpc/kernel/time.c | 29 ++++++++++++++--------------- 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index f5cbfe5efd25..f80cce0e3899 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -615,23 +615,22 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(timer_interrupt) return; } - /* Conditionally hard-enable interrupts. */ - if (should_hard_irq_enable()) { - /* - * Ensure a positive value is written to the decrementer, or - * else some CPUs will continue to take decrementer exceptions. - * When the PPC_WATCHDOG (decrementer based) is configured, - * keep this at most 31 bits, which is about 4 seconds on most - * systems, which gives the watchdog a chance of catching timer - * interrupt hard lockups. - */ - if (IS_ENABLED(CONFIG_PPC_WATCHDOG)) - set_dec(0x7fffffff); - else - set_dec(decrementer_max); + /* + * Ensure a positive value is written to the decrementer, or + * else some CPUs will continue to take decrementer exceptions. + * When the PPC_WATCHDOG (decrementer based) is configured, + * keep this at most 31 bits, which is about 4 seconds on most + * systems, which gives the watchdog a chance of catching timer + * interrupt hard lockups. + */ + if (IS_ENABLED(CONFIG_PPC_WATCHDOG)) + set_dec(0x7fffffff); + else + set_dec(decrementer_max); + /* Conditionally hard-enable interrupts. */ + if (should_hard_irq_enable()) do_hard_irq_enable(); - } #if defined(CONFIG_PPC32) && defined(CONFIG_PPC_PMAC) if (atomic_read(&ppc_n_lost_interrupts) != 0)