From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D35EF33CC7; Fri, 24 Nov 2023 18:36:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="t5Vqr9A+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6309EC433C8; Fri, 24 Nov 2023 18:36:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700851018; bh=kmpwIOJpM7H/mLSAegnIwFskjQCoH8l3SaYWRtm1kXQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=t5Vqr9A+JgtvITBmUSmdxB5/UBxqDv+ibENVVFI5jzNFESw8pniRR80VnxOsGI57y Ao1Croar07VnsIXbBoy00zG5kQdnCoGJGGhdONYAXOm8N4GsupT/kM3gt/syCXcGKd /VkZGVBS3hL0HWt2EqJGnZU3n/dkPOBlza7/6IoQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Igor Raits , Bagas Sanjaya , "Peter Zijlstra (Intel)" , Hao Jia Subject: [PATCH 6.5 281/491] sched/core: Fix RQCF_ACT_SKIP leak Date: Fri, 24 Nov 2023 17:48:37 +0000 Message-ID: <20231124172033.022576144@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231124172024.664207345@linuxfoundation.org> References: <20231124172024.664207345@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hao Jia commit 5ebde09d91707a4a9bec1e3d213e3c12ffde348f upstream. Igor Raits and Bagas Sanjaya report a RQCF_ACT_SKIP leak warning. This warning may be triggered in the following situations: CPU0 CPU1 __schedule() *rq->clock_update_flags <<= 1;* unregister_fair_sched_group() pick_next_task_fair+0x4a/0x410 destroy_cfs_bandwidth() newidle_balance+0x115/0x3e0 for_each_possible_cpu(i) *i=0* rq_unpin_lock(this_rq, rf) __cfsb_csd_unthrottle() raw_spin_rq_unlock(this_rq) rq_lock(*CPU0_rq*, &rf) rq_clock_start_loop_update() rq->clock_update_flags & RQCF_ACT_SKIP <-- raw_spin_rq_lock(this_rq) The purpose of RQCF_ACT_SKIP is to skip the update rq clock, but the update is very early in __schedule(), but we clear RQCF_*_SKIP very late, causing it to span that gap above and triggering this warning. In __schedule() we can clear the RQCF_*_SKIP flag immediately after update_rq_clock() to avoid this RQCF_ACT_SKIP leak warning. And set rq->clock_update_flags to RQCF_UPDATED to avoid rq->clock_update_flags < RQCF_ACT_SKIP warning that may be triggered later. Fixes: ebb83d84e49b ("sched/core: Avoid multiple calling update_rq_clock() in __cfsb_csd_unthrottle()") Closes: https://lore.kernel.org/all/20230913082424.73252-1-jiahao.os@bytedance.com Reported-by: Igor Raits Reported-by: Bagas Sanjaya Suggested-by: Peter Zijlstra (Intel) Signed-off-by: Hao Jia Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/a5dd536d-041a-2ce9-f4b7-64d8d85c86dc@gmail.com Signed-off-by: Greg Kroah-Hartman --- kernel/sched/core.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5377,8 +5377,6 @@ context_switch(struct rq *rq, struct tas /* switch_mm_cid() requires the memory barriers above. */ switch_mm_cid(rq, prev, next); - rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); - prepare_lock_switch(rq, next, rf); /* Here we just switch the register state and the stack. */ @@ -6634,6 +6632,7 @@ static void __sched notrace __schedule(u /* Promote REQ to ACT */ rq->clock_update_flags <<= 1; update_rq_clock(rq); + rq->clock_update_flags = RQCF_UPDATED; switch_count = &prev->nivcsw; @@ -6713,8 +6712,6 @@ static void __sched notrace __schedule(u /* Also unlocks the rq: */ rq = context_switch(rq, prev, next, &rf); } else { - rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); - rq_unpin_lock(rq, &rf); __balance_callbacks(rq); raw_spin_rq_unlock_irq(rq);