From patchwork Thu Mar 23 16:18:30 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13185821 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B592C6FD1C for ; Thu, 23 Mar 2023 16:18:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229976AbjCWQSj (ORCPT ); Thu, 23 Mar 2023 12:18:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51454 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231436AbjCWQSh (ORCPT ); Thu, 23 Mar 2023 12:18:37 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7221727D43; Thu, 23 Mar 2023 09:18:33 -0700 (PDT) Date: Thu, 23 Mar 2023 17:18:30 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1679588312; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=J7HfOv4nohJ8yEKD7u+zI1jmEYsLBtE90jZ4cY+f0kU=; b=d9nP8oUh2EGPPSGxuNz+gKh7DykB/H6wIvVY2Gh5XyZjFTYHdMB7sA1Aa0jwBaaVTytcb7 bzTs4hYVhNuPR+dPmUxWk4h4Y87xVQLRcnTg9DH6lEcJvhH4N+bMsFutht0K5y5HAlnUmz /gtzoeF752aw1t557zymOMPyFEcEtv1Vhzuz1wEImnveogEkb1yIjHYnoZ/JewoYYNLZbk 35jMxZkX9eZH8AZ034RZepBlSZhCjPXfdU+fYGYiIkQwXKX7d+FqALEmpLnlRXishX0hB8 uhy1CiUM7cevVYWaBSqllFcdrL1qX2A8OymzcMrLFcAyJiRACIVfKmLmQ0i04Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1679588312; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=J7HfOv4nohJ8yEKD7u+zI1jmEYsLBtE90jZ4cY+f0kU=; b=Lp8ojpwJQx+FPnLc6Ueru8ooKVl7koqKY2tCxQPFnorgg7PNfKQ89o15TFHjtsXd0/Ht0P ZbioBM2QXvvAxQBA== From: Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Cc: Jens Axboe , Mike Galbraith , Minchan Kim , Sergey Senozhatsky , Thomas Gleixner Subject: [PATCH] zram: Replace bit spinlocks with spinlock_t for PREEMPT_RT. Message-ID: <20230323161830.jFbWCosd@linutronix.de> MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Mike Galbraith The bit spinlock disables preemption. The spinlock_t lock becomes a sleeping lock on PREEMPT_RT and it can not be acquired in this context. In this locked section, zs_free() acquires a zs_pool::lock, and there is access to zram::wb_limit_lock. Use a spinlock_t on PREEMPT_RT for locking and set/ clear ZRAM_LOCK bit after the lock has been acquired/ dropped. Signed-off-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior Link: https://lkml.kernel.org/r/YqIbMuHCPiQk+Ac2@linutronix.de --- I'm simply forwarding Mike's patch here. The other alternative is to let the driver depend on !PREEMPT_RT. I can't tell likely it is that this driver is used. Mike most likely stumbled upon it while running LTP. drivers/block/zram/zram_drv.c | 36 ++++++++++++++++++++++++++++++++++++ drivers/block/zram/zram_drv.h | 3 +++ 2 files changed, 39 insertions(+) --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -57,6 +57,40 @@ static void zram_free_page(struct zram * static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, u32 index, int offset, struct bio *bio); +#ifdef CONFIG_PREEMPT_RT +static void zram_meta_init_table_locks(struct zram *zram, size_t num_pages) +{ + size_t index; + + for (index = 0; index < num_pages; index++) + spin_lock_init(&zram->table[index].lock); +} + +static int zram_slot_trylock(struct zram *zram, u32 index) +{ + int ret; + + ret = spin_trylock(&zram->table[index].lock); + if (ret) + __set_bit(ZRAM_LOCK, &zram->table[index].flags); + return ret; +} + +static void zram_slot_lock(struct zram *zram, u32 index) +{ + spin_lock(&zram->table[index].lock); + __set_bit(ZRAM_LOCK, &zram->table[index].flags); +} + +static void zram_slot_unlock(struct zram *zram, u32 index) +{ + __clear_bit(ZRAM_LOCK, &zram->table[index].flags); + spin_unlock(&zram->table[index].lock); +} + +#else + +static void zram_meta_init_table_locks(struct zram *zram, size_t num_pages) { } static int zram_slot_trylock(struct zram *zram, u32 index) { @@ -72,6 +106,7 @@ static void zram_slot_unlock(struct zram { bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags); } +#endif static inline bool init_done(struct zram *zram) { @@ -1311,6 +1346,7 @@ static bool zram_meta_alloc(struct zram if (!huge_class_size) huge_class_size = zs_huge_class_size(zram->mem_pool); + zram_meta_init_table_locks(zram, num_pages); return true; } --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -69,6 +69,9 @@ struct zram_table_entry { unsigned long element; }; unsigned long flags; +#ifdef CONFIG_PREEMPT_RT + spinlock_t lock; +#endif #ifdef CONFIG_ZRAM_MEMORY_TRACKING ktime_t ac_time; #endif