From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D9EA53AD52D for ; Tue, 21 Apr 2026 11:14:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776770067; cv=none; b=diKuUfvR154qz1nmZkZwbbMqFkMfJhMZVGic8/8JXQUhLLkAtu4kS1aKJY4AyZCV2Z3k2oJlQyJFn3IvNUXr2aXJuIk6cwckQijMrtbxT25oCCPMXfxxkvHADKuC+wvgadvOBn1X5UhS9XhxI9ikmDq2yqQcZFr7nNthe2qE7ek= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776770067; c=relaxed/simple; bh=5K0ZVS0APQLN57oZrYXWKqsh6xQ69IJ2RExLu8gmfz0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YEHRDMhoXhf+363b/y+dbj1BAchBTeQuZDSpTMkDb5b8hZkILXJ/JZKGADbC0HLSXkjFq6L6Ny88DiB4CfsX3ETSwWFQtSamCr4cy3jEioykvhyrruNKl+TphSw90smdp8uQipsSDLwK3Hh2B0BU5A2bO22z1zfPKHkkPP+OFpw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=QTiCJyen; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="QTiCJyen" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8A01A25E0; Tue, 21 Apr 2026 04:14:18 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.1.197.6]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BA6363FE87; Tue, 21 Apr 2026 04:14:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1776770064; bh=5K0ZVS0APQLN57oZrYXWKqsh6xQ69IJ2RExLu8gmfz0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QTiCJyenB24sUeYUjHQyC7n1AgtEH05T2pEbfVIInu1UVOZhU1T10YbLtA5tBpJpZ JsLO70oRpbQbpRbqBmuHIiZzJmIQKmR60SosyXWUTNVetOiw0MS9oVrtAMGgzJ4z2C UBnn3fV+2cTQ3w0U5aRt752bpA/UEAct1rFHAwLQ= Date: Tue, 21 Apr 2026 12:14:20 +0100 From: Yeoreum Yun To: Leo Yan Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, suzuki.poulose@arm.com, mike.leach@arm.com, james.clark@linaro.org, alexander.shishkin@linux.intel.com, jie.gan@oss.qualcomm.com Subject: Re: [PATCH v5 07/12] coresight: etm4x: fix inconsistencies with sysfs configuration Message-ID: References: <20260415165528.3369607-1-yeoreum.yun@arm.com> <20260415165528.3369607-8-yeoreum.yun@arm.com> <20260421104601.GB929984@e132581.arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260421104601.GB929984@e132581.arm.com> On Tue, Apr 21, 2026 at 11:46:01AM +0100, Leo Yan wrote: > On Wed, Apr 15, 2026 at 05:55:23PM +0100, Yeoreum Yun wrote: > > The current ETM4x configuration via sysfs can lead to > > several inconsistencies: > > > > - If the configuration is modified via sysfs while a perf session is > > active, the running configuration may differ before a sched-out and > > after a subsequent sched-in. > > > > - If a perf session and a sysfs session enable tracing concurrently, > > the configuration from configfs may become corrupted. > > I think this happens because the sysfs path calls > cscfg_csdev_enable_active_config() without first acquiring the mode, > allowing a perf session to acquire the mode and call the same function > concurrently. Yes. That's why this patch changes to call cscfg_csdev_enable_active_config() after taking a mode. > > > - There is a risk of corrupting drvdata->config if a perf session enables > > tracing while cscfg_csdev_disable_active_config() is being handled in > > etm4_disable_sysfs(). > > Similiar to above, cscfg_csdev_disable_active_config() is not > protected in etm4_disable_sysfs(). This is not true. at the time of etm4_disable_sysfs() "mode" is already taken (whether sysfs or perf). In this situation, it's enough to call cscfg_csdev_disable_active_config() before chaning mode to DISABLED. > > > To resolve these issues, separate the configuration into: > > > > - active_config: the configuration applied to the current session > > - config: the configuration set via sysfs > > > > Additionally: > > > > - Apply the configuration from configfs after taking the appropriate mode. > > > > - Since active_config and related fields are accessed only by the local CPU > > in etm4_enable/disable_sysfs_smp_call() (similar to perf enable/disable), > > remove the lock/unlock from the sysfs enable/disable path and > > startup/dying_cpu except when to access config fields. > > > > Signed-off-by: Yeoreum Yun > > --- > > .../hwtracing/coresight/coresight-etm4x-cfg.c | 2 +- > > .../coresight/coresight-etm4x-core.c | 107 ++++++++++-------- > > drivers/hwtracing/coresight/coresight-etm4x.h | 2 + > > 3 files changed, 63 insertions(+), 48 deletions(-) > > > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c > > index d14d7c8a23e5..0553771d04e7 100644 > > --- a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c > > +++ b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c > > @@ -47,7 +47,7 @@ static int etm4_cfg_map_reg_offset(struct etmv4_drvdata *drvdata, > > struct cscfg_regval_csdev *reg_csdev, u32 offset) > > { > > int err = -EINVAL, idx; > > - struct etmv4_config *drvcfg = &drvdata->config; > > + struct etmv4_config *drvcfg = &drvdata->active_config; > > u32 off_mask; > > > > if (((offset >= TRCEVENTCTL0R) && (offset <= TRCVIPCSSCTLR)) || > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c > > index b199aebbdb60..15aaf4a898e1 100644 > > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c > > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c > > @@ -245,6 +245,10 @@ void etm4_release_trace_id(struct etmv4_drvdata *drvdata) > > > > struct etm4_enable_arg { > > struct etmv4_drvdata *drvdata; > > + unsigned long cfg_hash; > > + int preset; > > Since smp call cannot directly call cscfg_config_sysfs_get_active_cfg() > due to it runs in atomic context but ...active_cfg() tries to acquire > mutex. So we firstly retrieve pass 'cfg_hash' and 'preset' in sleepable > context and deliver them to the SMP call. > > After coresight cfg refactoring, we should remove cfg_hash/preset from > ETM driver, the ETM driver only needs to retrieve register list and can > do this in smp call. > > Before we finish cfg refactoring, it is fine for me to add these two > parameters into etm4_enable_arg. Sound good and interting to refactorying. but as you said this is fine for fixing a bug purpose. > > > + u8 trace_id; > > Can we add 'path' instead ? The SMP call can retrieve path->trace_id. > This can benefit for future clean up (e.g., we can store config into > path so we can retrieve config from path pointer), and this allows us > for further refactoring to unify etm4_enable_sysfs_smp_call() and > etm4_enable_perf(). Okay. I'll change it with the path. > > > + struct etmv4_config config; > > We don't need this. We can defer to get drvdata->config in SMP call. This is not true ane make a situation more complex. If we get config in SMP call, that would be a problem when some user is trying to modify config. IOW, while user modifying config via sysfs, and SMP call happens, it makes a dead lock. so for this if we try to grab the lock in SMP call, we should change every sysfs raw_spin_lock() into raw_spin_lock_irqsave(). Instead of this it would be much clear and simpler to get config in here rather than to add some latencies via sysfs. > > > int rc; > > }; > > [...] > > > @@ -918,40 +946,29 @@ static int etm4_enable_sysfs(struct coresight_device *csdev, struct coresight_pa > > > > /* enable any config activated by configfs */ > > cscfg_config_sysfs_get_active_cfg(&cfg_hash, &preset); > > - if (cfg_hash) { > > - ret = cscfg_csdev_enable_active_config(csdev, cfg_hash, preset); > > - if (ret) { > > - etm4_release_trace_id(drvdata); > > - return ret; > > - } > > - } > > - > > - raw_spin_lock(&drvdata->spinlock); > > - > > - drvdata->trcid = path->trace_id; > > - > > - /* Tracer will never be paused in sysfs mode */ > > - drvdata->paused = false; > > > > /* > > * Executing etm4_enable_hw on the cpu whose ETM is being enabled > > * ensures that register writes occur when cpu is powered. > > */ > > arg.drvdata = drvdata; > > + arg.cfg_hash = cfg_hash; > > + arg.preset = preset; > > + arg.trace_id = path->trace_id; > > + > > + raw_spin_lock(&drvdata->spinlock); > > + arg.config = drvdata->config; > > + raw_spin_unlock(&drvdata->spinlock); > > Can we defer this in smp call ? And we can consolidate a bit Nope. Please see the above answer. > configurations, we can consider to use a separate patch for this. > > etm4x_apply_config(drvdata, event, hash, preset) > { > /* perf mode */ > if (event) { > etm4_parse_event_config(drvdata->csdev, event); > } else if (mode == CS_MODE_PERF) { > scoped_guard(raw_spinlock, &drvdata->spinlock) > &drvdata->active_config = drvdata->config; > } > > /* At the end, we always apply the config */ > cscfg_csdev_enable_active_config(drvdata->csdev, hash, preset); > } etm4_parse_event_config() already calls cscfg_csdev_enable_active_config() But this is refactorying perspective. I think we can postpone this via another patchset. > > > + > > ret = smp_call_function_single(drvdata->cpu, > > etm4_enable_sysfs_smp_call, &arg, 1); > > if (!ret) > > ret = arg.rc; > > if (!ret) > > - drvdata->sticky_enable = true; > > - > > - if (ret) > > + dev_dbg(&csdev->dev, "ETM tracing enabled\n"); > > + else > > etm4_release_trace_id(drvdata); > > > > - raw_spin_unlock(&drvdata->spinlock); > > - > > - if (!ret) > > - dev_dbg(&csdev->dev, "ETM tracing enabled\n"); > > return ret; > > } > > > > @@ -1038,7 +1055,7 @@ static void etm4_disable_hw(struct etmv4_drvdata *drvdata) > > { > > u32 control; > > const struct etmv4_caps *caps = &drvdata->caps; > > - struct etmv4_config *config = &drvdata->config; > > + struct etmv4_config *config = &drvdata->active_config; > > struct coresight_device *csdev = drvdata->csdev; > > struct csdev_access *csa = &csdev->access; > > int i; > > @@ -1074,6 +1091,8 @@ static void etm4_disable_sysfs_smp_call(void *info) > > > > etm4_disable_hw(drvdata); > > > > + cscfg_csdev_disable_active_config(drvdata->csdev); > > + > > coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED); > > } > > > > @@ -1124,7 +1143,6 @@ static void etm4_disable_sysfs(struct coresight_device *csdev) > > * DYING hotplug callback is serviced by the ETM driver. > > */ > > cpus_read_lock(); > > - raw_spin_lock(&drvdata->spinlock); > > > > /* > > * Executing etm4_disable_hw on the cpu whose ETM is being disabled > > @@ -1133,10 +1151,6 @@ static void etm4_disable_sysfs(struct coresight_device *csdev) > > smp_call_function_single(drvdata->cpu, etm4_disable_sysfs_smp_call, > > drvdata, 1); > > > > - raw_spin_unlock(&drvdata->spinlock); > > - > > - cscfg_csdev_disable_active_config(csdev); > > - > > cpus_read_unlock(); > > > > /* > > @@ -1379,6 +1393,7 @@ static void etm4_init_arch_data(void *info) > > struct etm4_init_arg *init_arg = info; > > struct etmv4_drvdata *drvdata; > > struct etmv4_caps *caps; > > + struct etmv4_config *config; > > struct csdev_access *csa; > > struct device *dev = init_arg->dev; > > int i; > > @@ -1386,6 +1401,7 @@ static void etm4_init_arch_data(void *info) > > drvdata = dev_get_drvdata(init_arg->dev); > > caps = &drvdata->caps; > > csa = init_arg->csa; > > + config = &drvdata->active_config; > > Should we init drvdata->config instead so make it has sane values ? > > In other words, drvdata->active_config are always set at the runtime, > so don't need to init it at all, right? No. at least when the initialise, I think we should fill the its contesnt with the "etm4_set_default()". That's why the consequence call etm4_set_default() called with active_config and config is coped with the default configutation. Thanks. -- Sincerely, Yeoreum Yun