From nobody Sun Feb 8 09:37:42 2026 Received: from canpmsgout01.his.huawei.com (canpmsgout01.his.huawei.com [113.46.200.216]) (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 43E52358D17 for ; Tue, 11 Nov 2025 12:22:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.216 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762863725; cv=none; b=KSgCUIsLX0CsEJbzVsNto3mOwPCmVjJ2hbvboe3qmh9UkSy1tgBOQiOGmvrT3JpjiKAox72CQOj2HgVGcTRdA7rIPkRyQFEsd2TFJh7CRdYprORvRxSkHQ2U/nEWsfd1QsgiZmTSCM0OWsMRMEZw11yar4ErXdKFtRwTGy2m4fo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762863725; c=relaxed/simple; bh=zgiRBQQ7joUu4LKi8ZQiRh7n4uBaFjcvMvGAaP2mNZk=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=bs4a6N0Y6TwGHrrQKkgjCalEFdjO0Oc9CX5h1/jIlaYf4WMPaQZlXA3HMQA3lU7btxptxX2xDBGfwgdPL+zUXsnuVMo1AI6MqYlOoHfceFH0mpMQX6iJpdPyf0OLlHKGlRZEqxOLa5mckORucfAKs24dTo8l4xohYFOOA2jfXRs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=h-partners.com; spf=pass smtp.mailfrom=h-partners.com; dkim=pass (1024-bit key) header.d=h-partners.com header.i=@h-partners.com header.b=jTTVdMyq; arc=none smtp.client-ip=113.46.200.216 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=h-partners.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=h-partners.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=h-partners.com header.i=@h-partners.com header.b="jTTVdMyq" dkim-signature: v=1; a=rsa-sha256; d=h-partners.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=UVKgAmWWkoiDmP3wvJgAABngR9HVzXoceStVuahg8hY=; b=jTTVdMyqy3bwE4uRO9tMuFpv+qCp8nCvJk3YAYKOU3rhHukadotGb6KZ2WzvrAe7ntAjikih5 0FokWLKlH6qyiHINXgwUulJ0YNEKuafKo8BG/INOuKmecrfeqOqHQ6ntzzyJXPXX7n3pv53wz+G 0T7FIMHCnNAUSlnOiLeu42I= Received: from mail.maildlp.com (unknown [172.19.163.48]) by canpmsgout01.his.huawei.com (SkyGuard) with ESMTPS id 4d5Qbh1vRKz1T4Ff; Tue, 11 Nov 2025 20:20:32 +0800 (CST) Received: from dggemv712-chm.china.huawei.com (unknown [10.1.198.32]) by mail.maildlp.com (Postfix) with ESMTPS id 586651800B1; Tue, 11 Nov 2025 20:21:54 +0800 (CST) Received: from kwepemn500004.china.huawei.com (7.202.194.145) by dggemv712-chm.china.huawei.com (10.1.198.32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 11 Nov 2025 20:21:54 +0800 Received: from localhost.localdomain (10.50.163.32) by kwepemn500004.china.huawei.com (7.202.194.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 11 Nov 2025 20:21:51 +0800 From: Junhao He To: , , , , , CC: , , , , , Subject: [PATCH v4 1/3] coresight: tmc: Add missing doc including reading and etr_mode of struct tmc_drvdata Date: Tue, 11 Nov 2025 20:21:47 +0800 Message-ID: <20251111122149.1981162-2-hejunhao3@h-partners.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20251111122149.1981162-1-hejunhao3@h-partners.com> References: <20251111122149.1981162-1-hejunhao3@h-partners.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To kwepemn500004.china.huawei.com (7.202.194.145) Content-Type: text/plain; charset="utf-8" From: Yicong Yang tmc_drvdata::reading is used to indicate whether a reading process is performed through /dev/xyz.tmc. tmc_drvdata::etr_mode is used to store the Coresight TMC-ETR buffer mode selected by the user. Document them. Reviewed-by: James Clark Signed-off-by: Yicong Yang Signed-off-by: Junhao He Reviewed-by: Leo Yan Signed-off-by: Junhao He --- drivers/hwtracing/coresight/coresight-tmc.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracin= g/coresight/coresight-tmc.h index cbb4ba439158..dd6c80fbae00 100644 --- a/drivers/hwtracing/coresight/coresight-tmc.h +++ b/drivers/hwtracing/coresight/coresight-tmc.h @@ -221,6 +221,7 @@ struct tmc_resrv_buf { * @pid: Process ID of the process that owns the session that is using * this component. For example this would be the pid of the Perf * process. + * @reading: buffer's in the reading through "/dev/xyz.tmc" entry * @stop_on_flush: Stop on flush trigger user configuration. * @buf: Snapshot of the trace data for ETF/ETB. * @etr_buf: details of buffer used in TMC-ETR @@ -233,6 +234,7 @@ struct tmc_resrv_buf { * @trigger_cntr: amount of words to store after a trigger. * @etr_caps: Bitmask of capabilities of the TMC ETR, inferred from the * device configuration register (DEVID) + * @etr_mode: User preferred mode of the ETR device, default auto mode. * @idr: Holds etr_bufs allocated for this ETR. * @idr_mutex: Access serialisation for idr. * @sysfs_buf: SYSFS buffer for ETR. --=20 2.33.0 From nobody Sun Feb 8 09:37:42 2026 Received: from canpmsgout06.his.huawei.com (canpmsgout06.his.huawei.com [113.46.200.221]) (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 176F43396E4 for ; 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Tue, 11 Nov 2025 20:21:54 +0800 (CST) Received: from kwepemn500004.china.huawei.com (7.202.194.145) by dggemv712-chm.china.huawei.com (10.1.198.32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 11 Nov 2025 20:21:54 +0800 Received: from localhost.localdomain (10.50.163.32) by kwepemn500004.china.huawei.com (7.202.194.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 11 Nov 2025 20:21:52 +0800 From: Junhao He To: , , , , , CC: , , , , , Subject: [PATCH v4 2/3] coresight: tmc: refactor the tmc-etr mode setting to avoid race conditions Date: Tue, 11 Nov 2025 20:21:48 +0800 Message-ID: <20251111122149.1981162-3-hejunhao3@h-partners.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20251111122149.1981162-1-hejunhao3@h-partners.com> References: <20251111122149.1981162-1-hejunhao3@h-partners.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To kwepemn500004.china.huawei.com (7.202.194.145) Content-Type: text/plain; charset="utf-8" From: Junhao He When trying to run perf and sysfs mode simultaneously, the WARN_ON() in tmc_etr_enable_hw() is triggered sometimes: WARNING: CPU: 42 PID: 3911571 at drivers/hwtracing/coresight/coresight-tmc= -etr.c:1060 tmc_etr_enable_hw+0xc0/0xd8 [coresight_tmc] [..snip..] Call trace: tmc_etr_enable_hw+0xc0/0xd8 [coresight_tmc] (P) tmc_enable_etr_sink+0x11c/0x250 [coresight_tmc] (L) tmc_enable_etr_sink+0x11c/0x250 [coresight_tmc] coresight_enable_path+0x1c8/0x218 [coresight] coresight_enable_sysfs+0xa4/0x228 [coresight] enable_source_store+0x58/0xa8 [coresight] dev_attr_store+0x20/0x40 sysfs_kf_write+0x4c/0x68 kernfs_fop_write_iter+0x120/0x1b8 vfs_write+0x2c8/0x388 ksys_write+0x74/0x108 __arm64_sys_write+0x24/0x38 el0_svc_common.constprop.0+0x64/0x148 do_el0_svc+0x24/0x38 el0_svc+0x3c/0x130 el0t_64_sync_handler+0xc8/0xd0 el0t_64_sync+0x1ac/0x1b0 ---[ end trace 0000000000000000 ]--- Since the sysfs buffer allocation and the hardware enablement is not in the same critical region, it's possible to race with the perf mode: [sysfs mode] [perf mode] tmc_etr_get_sysfs_buffer() spin_lock(&drvdata->spinlock) [sysfs buffer allocation] spin_unlock(&drvdata->spinlock) spin_lock(&drvdata->spinlock) tmc_etr_enable_hw() drvdata->etr_buf =3D etr_perf->etr_buf spin_unlock(&drvdata->spinlock) spin_lock(&drvdata->spinlock) tmc_etr_enable_hw() WARN_ON(drvdata->etr_buf) // WARN sicne etr_buf initialized at the perf side spin_unlock(&drvdata->spinlock) A race condition is introduced here, perf always prioritizes execution, and warnings can lead to concerns about potential hidden bugs, such as getting out of sync. To fix this, configure the tmc-etr mode before invoking enable_etr_perf() or enable_etr_sysfs(), explicitly check if the tmc-etr sink is already enabled in a different mode, and simplily the setup and checks for "mode". To prevent race conditions between mode transitions. Fixes: 296b01fd106e ("coresight: Refactor out buffer allocation function fo= r ETR") Reported-by: Yicong Yang Closes: https://lore.kernel.org/linux-arm-kernel/20241202092419.11777-2-yan= gyicong@huawei.com/ Signed-off-by: Junhao He Tested-by: Yicong Yang Signed-off-by: Junhao He --- .../hwtracing/coresight/coresight-tmc-etr.c | 106 +++++++++--------- 1 file changed, 55 insertions(+), 51 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtr= acing/coresight/coresight-tmc-etr.c index b07fcdb3fe1a..fe1d5e8a0d2b 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -1263,11 +1263,6 @@ static struct etr_buf *tmc_etr_get_sysfs_buffer(stru= ct coresight_device *csdev) raw_spin_lock_irqsave(&drvdata->spinlock, flags); } =20 - if (drvdata->reading || coresight_get_mode(csdev) =3D=3D CS_MODE_PERF) { - ret =3D -EBUSY; - goto out; - } - /* * If we don't have a buffer or it doesn't match the requested size, * use the buffer allocated above. Otherwise reuse the existing buffer. @@ -1278,7 +1273,6 @@ static struct etr_buf *tmc_etr_get_sysfs_buffer(struc= t coresight_device *csdev) drvdata->sysfs_buf =3D new_buf; } =20 -out: raw_spin_unlock_irqrestore(&drvdata->spinlock, flags); =20 /* Free memory outside the spinlock if need be */ @@ -1289,7 +1283,7 @@ static struct etr_buf *tmc_etr_get_sysfs_buffer(struc= t coresight_device *csdev) =20 static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev) { - int ret =3D 0; + int ret; unsigned long flags; struct tmc_drvdata *drvdata =3D dev_get_drvdata(csdev->dev.parent); struct etr_buf *sysfs_buf =3D tmc_etr_get_sysfs_buffer(csdev); @@ -1299,23 +1293,10 @@ static int tmc_enable_etr_sink_sysfs(struct coresig= ht_device *csdev) =20 raw_spin_lock_irqsave(&drvdata->spinlock, flags); =20 - /* - * In sysFS mode we can have multiple writers per sink. Since this - * sink is already enabled no memory is needed and the HW need not be - * touched, even if the buffer size has changed. - */ - if (coresight_get_mode(csdev) =3D=3D CS_MODE_SYSFS) { - csdev->refcnt++; - goto out; - } - ret =3D tmc_etr_enable_hw(drvdata, sysfs_buf); - if (!ret) { - coresight_set_mode(csdev, CS_MODE_SYSFS); + if (!ret) csdev->refcnt++; - } =20 -out: raw_spin_unlock_irqrestore(&drvdata->spinlock, flags); =20 if (!ret) @@ -1729,39 +1710,24 @@ static int tmc_enable_etr_sink_perf(struct coresigh= t_device *csdev, void *data) { int rc =3D 0; pid_t pid; - unsigned long flags; struct tmc_drvdata *drvdata =3D dev_get_drvdata(csdev->dev.parent); struct perf_output_handle *handle =3D data; struct etr_perf_buffer *etr_perf =3D etm_perf_sink_config(handle); =20 - raw_spin_lock_irqsave(&drvdata->spinlock, flags); - /* Don't use this sink if it is already claimed by sysFS */ - if (coresight_get_mode(csdev) =3D=3D CS_MODE_SYSFS) { - rc =3D -EBUSY; - goto unlock_out; - } - - if (WARN_ON(!etr_perf || !etr_perf->etr_buf)) { - rc =3D -EINVAL; - goto unlock_out; - } + if (WARN_ON(!etr_perf || !etr_perf->etr_buf)) + return -EINVAL; =20 /* Get a handle on the pid of the session owner */ pid =3D etr_perf->pid; =20 /* Do not proceed if this device is associated with another session */ - if (drvdata->pid !=3D -1 && drvdata->pid !=3D pid) { - rc =3D -EBUSY; - goto unlock_out; - } + if (drvdata->pid !=3D -1 && drvdata->pid !=3D pid) + return -EBUSY; =20 - /* - * No HW configuration is needed if the sink is already in - * use for this session. - */ + /* The sink is already in use for this session */ if (drvdata->pid =3D=3D pid) { csdev->refcnt++; - goto unlock_out; + return rc; } =20 rc =3D tmc_etr_enable_hw(drvdata, etr_perf->etr_buf); @@ -1773,22 +1739,60 @@ static int tmc_enable_etr_sink_perf(struct coresigh= t_device *csdev, void *data) csdev->refcnt++; } =20 -unlock_out: - raw_spin_unlock_irqrestore(&drvdata->spinlock, flags); return rc; } =20 static int tmc_enable_etr_sink(struct coresight_device *csdev, enum cs_mode mode, void *data) { - switch (mode) { - case CS_MODE_SYSFS: - return tmc_enable_etr_sink_sysfs(csdev); - case CS_MODE_PERF: - return tmc_enable_etr_sink_perf(csdev, data); - default: - return -EINVAL; + struct tmc_drvdata *drvdata =3D dev_get_drvdata(csdev->dev.parent); + int rc; + +retry: + scoped_guard(raw_spinlock_irqsave, &drvdata->spinlock) { + if (coresight_get_mode(csdev) !=3D CS_MODE_DISABLED && + coresight_get_mode(csdev) !=3D mode) + return -EBUSY; + + switch (mode) { + case CS_MODE_SYSFS: + if (drvdata->reading) + return -EBUSY; + + if (csdev->refcnt) { + /* The sink is already enabled via sysfs */ + csdev->refcnt++; + return 0; + } + + /* + * A sysfs session is currently enabling ETR, preventing + * a second sysfs process from repeatedly triggering the + * enable procedure. + */ + if (coresight_get_mode(csdev) =3D=3D CS_MODE_SYSFS && !csdev->refcnt) + goto retry; + + /* + * Set ETR to sysfs mode before it is fully enabled, to + * prevent race conditions during mode transitions. + */ + coresight_set_mode(csdev, mode); + break; + case CS_MODE_PERF: + return tmc_enable_etr_sink_perf(csdev, data); + default: + return -EINVAL; + } + } + + rc =3D tmc_enable_etr_sink_sysfs(csdev); + if (rc) { + guard(raw_spinlock_irqsave)(&drvdata->spinlock); + coresight_set_mode(csdev, CS_MODE_DISABLED); } + + return rc; } =20 static int tmc_disable_etr_sink(struct coresight_device *csdev) --=20 2.33.0 From nobody Sun Feb 8 09:37:42 2026 Received: from canpmsgout02.his.huawei.com (canpmsgout02.his.huawei.com [113.46.200.217]) (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 BB1F32EBB87 for ; Tue, 11 Nov 2025 12:21:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.217 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762863720; cv=none; b=naiJfvF9VUidYzIPi7wSGV4OXmo8jMLorcMV51aDLNb1Ug9D5hCLRIWuh7AeRoPXbaMlZfJUVS6s+D8BOEoBmFCymdyCAXN6W6o6oNoUC9eo8klADyk4PkIVFWWSTVtxO60eLMihGVvKvjtwNxS1GSYVS3WUAtoaY/w19AsNkA8= ARC-Message-Signature: i=1; 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Tue, 11 Nov 2025 20:21:52 +0800 From: Junhao He To: , , , , , CC: , , , , , Subject: [PATCH v4 3/3] coresight: tmc: Decouple the perf buffer allocation from sysfs mode Date: Tue, 11 Nov 2025 20:21:49 +0800 Message-ID: <20251111122149.1981162-4-hejunhao3@h-partners.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20251111122149.1981162-1-hejunhao3@h-partners.com> References: <20251111122149.1981162-1-hejunhao3@h-partners.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To kwepemn500004.china.huawei.com (7.202.194.145) Content-Type: text/plain; charset="utf-8" From: Yicong Yang Currently the perf buffer allocation follows the below logic: - if the required AUX buffer size if larger, allocate the buffer with the required size - otherwise allocate the size reference to the sysfs buffer size This is not useful as we only collect to one AUX data, so just try to allocate the buffer match the AUX buffer size. Suggested-by: Suzuki K Poulose Link: https://lore.kernel.org/linux-arm-kernel/df8967cd-2157-46a2-97d9-a1ae= a883cf63@arm.com/ Signed-off-by: Yicong Yang Signed-off-by: Junhao He Signed-off-by: Junhao He --- .../hwtracing/coresight/coresight-tmc-etr.c | 30 ++++++------------- 1 file changed, 9 insertions(+), 21 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtr= acing/coresight/coresight-tmc-etr.c index fe1d5e8a0d2b..c2ba004a25fe 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -1327,9 +1327,7 @@ EXPORT_SYMBOL_GPL(tmc_etr_get_buffer); =20 /* * alloc_etr_buf: Allocate ETR buffer for use by perf. - * The size of the hardware buffer is dependent on the size configured - * via sysfs and the perf ring buffer size. We prefer to allocate the - * largest possible size, scaling down the size by half until it + * Allocate the largest possible size, scaling down the size by half until= it * reaches a minimum limit (1M), beyond which we give up. */ static struct etr_buf * @@ -1338,36 +1336,26 @@ alloc_etr_buf(struct tmc_drvdata *drvdata, struct p= erf_event *event, { int node; struct etr_buf *etr_buf; - unsigned long size; + ssize_t size; =20 node =3D (event->cpu =3D=3D -1) ? NUMA_NO_NODE : cpu_to_node(event->cpu); - /* - * Try to match the perf ring buffer size if it is larger - * than the size requested via sysfs. - */ - if ((nr_pages << PAGE_SHIFT) > drvdata->size) { - etr_buf =3D tmc_alloc_etr_buf(drvdata, ((ssize_t)nr_pages << PAGE_SHIFT), - 0, node, NULL); - if (!IS_ERR(etr_buf)) - goto done; - } + + /* Use the minimum limit if the required size is smaller */ + size =3D nr_pages << PAGE_SHIFT; + size =3D max_t(ssize_t, size, TMC_ETR_PERF_MIN_BUF_SIZE); =20 /* - * Else switch to configured size for this ETR - * and scale down until we hit the minimum limit. + * Try to allocate the required size for this ETR, if failed scale + * down until we hit the minimum limit. */ - size =3D drvdata->size; do { etr_buf =3D tmc_alloc_etr_buf(drvdata, size, 0, node, NULL); if (!IS_ERR(etr_buf)) - goto done; + return etr_buf; size /=3D 2; } while (size >=3D TMC_ETR_PERF_MIN_BUF_SIZE); =20 return ERR_PTR(-ENOMEM); - -done: - return etr_buf; } =20 static struct etr_buf * --=20 2.33.0