* [PATCH] coresight: Defer probe when the child dev is not probed @ 2022-02-28 13:31 Mao Jinlong 2022-02-28 14:51 ` Suzuki K Poulose 0 siblings, 1 reply; 7+ messages in thread From: Mao Jinlong @ 2022-02-28 13:31 UTC (permalink / raw) To: Mathieu Poirier, Suzuki K Poulose, Mike Leach, Leo Yan, Alexander Shishkin Cc: Mao Jinlong, coresight, linux-arm-kernel, linux-kernel, linux-arm-msm, Tingwei Zhang, Jinlong Mao, Yuanfang Zhang, Tao Zhang, Hao Zhang From: Mao Jinlong <jinlmao@qti.qualcomm.com> It is possible that when device probe, its child device is not probed. Then it will fail when add sysfs connection for the device. Make device defer probe when the child device is not probed. Signed-off-by: Mao Jinlong <jinlmao@qti.qualcomm.com> --- drivers/hwtracing/coresight/coresight-sysfs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c index 34d2a2d31d00..7df9eb59bf2c 100644 --- a/drivers/hwtracing/coresight/coresight-sysfs.c +++ b/drivers/hwtracing/coresight/coresight-sysfs.c @@ -73,8 +73,10 @@ int coresight_add_sysfs_link(struct coresight_sysfs_link *info) if (!info->orig || !info->target || !info->orig_name || !info->target_name) return -EINVAL; - if (!info->orig->has_conns_grp || !info->target->has_conns_grp) + if (!info->orig->has_conns_grp) return -EINVAL; + if (!info->target->has_conns_grp) + return -EPROBE_DEFER; /* first link orig->target */ ret = sysfs_add_link_to_group(&info->orig->dev.kobj, -- 2.17.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] coresight: Defer probe when the child dev is not probed 2022-02-28 13:31 [PATCH] coresight: Defer probe when the child dev is not probed Mao Jinlong @ 2022-02-28 14:51 ` Suzuki K Poulose [not found] ` <a63abe13-793e-323f-e214-1dd9826c8a9a@quicinc.com> 0 siblings, 1 reply; 7+ messages in thread From: Suzuki K Poulose @ 2022-02-28 14:51 UTC (permalink / raw) To: Mao Jinlong, Mathieu Poirier, Mike Leach, Leo Yan, Alexander Shishkin Cc: Mao Jinlong, coresight, linux-arm-kernel, linux-kernel, linux-arm-msm, Tingwei Zhang, Yuanfang Zhang, Tao Zhang, Hao Zhang Hi Jinlong On 28/02/2022 13:31, Mao Jinlong wrote: > From: Mao Jinlong <jinlmao@qti.qualcomm.com> > > It is possible that when device probe, its child device is not > probed. Then it will fail when add sysfs connection for the device. > Make device defer probe when the child device is not probed. Please could you a bit a more specific on the exact issue ? I don't see a problem with probe deferral right now, with coresight/next. For e.g., root@juno-server:~# lsmod Module Size Used by coresight 73728 0 root@juno-server:~# ls /sys/bus/coresight/devices/ root@juno-server:~# modprobe coresight-etm4x root@juno-server:~# lsmod Module Size Used by coresight_etm4x 81920 0 coresight 73728 1 coresight_etm4x root@juno-server:~# ls /sys/bus/coresight/devices/ etm0 etm1 -- Note etm2-etm5 doesn't appear -- root@juno-server:~# modprobe coresight-funnel root@juno-server:~# lsmod Module Size Used by coresight_funnel 20480 0 coresight_etm4x 81920 0 coresight 73728 2 coresight_etm4x,coresight_funnel root@juno-server:~# ls /sys/bus/coresight/devices/ etm0 etm1 -- Still don't appear --- root@juno-server:~# modprobe coresight-replicator root@juno-server:~# ls /sys/bus/coresight/devices/ etm0 etm1 root@juno-server:~# modprobe coresight-tmc -- At this stage, the devices automatically get probed and appear -- root@juno-server:~# ls /sys/bus/coresight/devices/ etm0 etm1 etm2 etm3 etm4 etm5 funnel0 funnel1 funnel2 tmc_etf0 tmc_etr0 root@juno-server:~# lsmod Module Size Used by coresight_tmc 40960 0 coresight_replicator 20480 0 coresight_funnel 20480 0 coresight_etm4x 81920 0 coresight 73728 4 coresight_tmc,coresight_etm4x,coresight_replicator,coresight_funnel So, my question is, what is this patch trying to solve ? Cheers Suzuki > > Signed-off-by: Mao Jinlong <jinlmao@qti.qualcomm.com> > --- > drivers/hwtracing/coresight/coresight-sysfs.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c > index 34d2a2d31d00..7df9eb59bf2c 100644 > --- a/drivers/hwtracing/coresight/coresight-sysfs.c > +++ b/drivers/hwtracing/coresight/coresight-sysfs.c > @@ -73,8 +73,10 @@ int coresight_add_sysfs_link(struct coresight_sysfs_link *info) > if (!info->orig || !info->target || > !info->orig_name || !info->target_name) > return -EINVAL; > - if (!info->orig->has_conns_grp || !info->target->has_conns_grp) > + if (!info->orig->has_conns_grp) > return -EINVAL; > + if (!info->target->has_conns_grp) > + return -EPROBE_DEFER; > > /* first link orig->target */ > ret = sysfs_add_link_to_group(&info->orig->dev.kobj, ^ permalink raw reply [flat|nested] 7+ messages in thread
[parent not found: <a63abe13-793e-323f-e214-1dd9826c8a9a@quicinc.com>]
* Re: [PATCH] coresight: Defer probe when the child dev is not probed [not found] ` <a63abe13-793e-323f-e214-1dd9826c8a9a@quicinc.com> @ 2022-03-01 13:15 ` Mike Leach 2022-03-01 13:30 ` Jinlong Mao 0 siblings, 1 reply; 7+ messages in thread From: Mike Leach @ 2022-03-01 13:15 UTC (permalink / raw) To: Jinlong Mao Cc: Suzuki K Poulose, Mathieu Poirier, Leo Yan, Alexander Shishkin, Mao Jinlong, coresight, linux-arm-kernel, linux-kernel, linux-arm-msm, Tingwei Zhang, Yuanfang Zhang, Tao Zhang, Hao Zhang Hi, On Tue, 1 Mar 2022 at 11:42, Jinlong Mao <quic_jinlmao@quicinc.com> wrote: > > On 2/28/2022 10:51 PM, Suzuki K Poulose wrote: > > Hi Jinlong > > On 28/02/2022 13:31, Mao Jinlong wrote: > > From: Mao Jinlong <jinlmao@qti.qualcomm.com> > > It is possible that when device probe, its child device is not > probed. Then it will fail when add sysfs connection for the device. > Make device defer probe when the child device is not probed. > > > Please could you a bit a more specific on the exact issue ? > I don't see a problem with probe deferral right now, with > coresight/next. > > For e.g., > > root@juno-server:~# lsmod > Module Size Used by > coresight 73728 0 > root@juno-server:~# ls /sys/bus/coresight/devices/ > root@juno-server:~# modprobe coresight-etm4x > root@juno-server:~# lsmod > Module Size Used by > coresight_etm4x 81920 0 > coresight 73728 1 coresight_etm4x > root@juno-server:~# ls /sys/bus/coresight/devices/ > etm0 etm1 > > -- Note etm2-etm5 doesn't appear -- > > root@juno-server:~# modprobe coresight-funnel > root@juno-server:~# lsmod > Module Size Used by > coresight_funnel 20480 0 > coresight_etm4x 81920 0 > coresight 73728 2 coresight_etm4x,coresight_funnel > root@juno-server:~# ls /sys/bus/coresight/devices/ > etm0 etm1 > > -- Still don't appear --- > > root@juno-server:~# modprobe coresight-replicator > root@juno-server:~# ls /sys/bus/coresight/devices/ > etm0 etm1 > root@juno-server:~# modprobe coresight-tmc > > -- At this stage, the devices automatically get probed and appear -- > root@juno-server:~# ls /sys/bus/coresight/devices/ > etm0 etm1 etm2 etm3 etm4 etm5 funnel0 funnel1 funnel2 tmc_etf0 tmc_etr0 > > > root@juno-server:~# lsmod > Module Size Used by > coresight_tmc 40960 0 > coresight_replicator 20480 0 > coresight_funnel 20480 0 > coresight_etm4x 81920 0 > coresight 73728 4 coresight_tmc,coresight_etm4x,coresight_replicator,coresight_funnel > > So, my question is, what is this patch trying to solve ? > > > Cheers > Suzuki > > Hi Suzuki, > > This issue happens when race condition happens. > The condition is that the device and its child_device's probe happens at the same time. > > For example: device0 and its child device device1. > Both of them are calling coresight_register function. device0 is calling coresight_fixup_device_conns. > device1 is waiting for device0 to release the coresight_mutex. Because device1's csdev node is allocated, > coresight_make_links will be called for device0. Then in coresight_add_sysfs_link, has_conns_grp is true > for device0, but has_conns_grp is false for device1 as has_conns_grp is set to true in coresight_create_conns_sysfs_group . > The probe of device0 will fail for at this condition. > > > struct coresight_device *coresight_register(struct coresight_desc *desc) > { > ......... > mutex_lock(&coresight_mutex); > > ret = coresight_create_conns_sysfs_group(csdev); > if (!ret) > ret = coresight_fixup_device_conns(csdev); > if (!ret) > ret = coresight_fixup_orphan_conns(csdev); > if (!ret && cti_assoc_ops && cti_assoc_ops->add) > cti_assoc_ops->add(csdev); > > mutex_unlock(&coresight_mutex); > > ......... > > } > > static int coresight_fixup_device_conns(struct coresight_device *csdev) > { > .......... > conn->child_dev = > coresight_find_csdev_by_fwnode(conn->child_fwnode); The issue appears to be a constraint hidden in the lower layers of the code. Would a better solution not be to alter the code here: if (conn->child_dev && conn->child_dev->has_conns_grp) { ... } else { csdev->orphan = true; } which would mean that the connection attempt would drop through to label the connection as an orphan, to be cleaned up by the child itself when it runs coresight_fixup_orphan_conns() Regards Mike > if (conn->child_dev) { > ret = coresight_make_links(csdev, conn, > > conn->child_dev); > > .......... > > } > > > int coresight_add_sysfs_link(struct coresight_sysfs_link *info) > { > ................ > if (!info->orig->has_conns_grp || !info->target->has_conns_grp) > return -EINVAL; > > > > The probe fail issue is reproduced with reboot stress test on our internal device. > > With the patch, the probe fail issue is not reproduced. > > Thanks > > Jinlong Mao > > > > Signed-off-by: Mao Jinlong <jinlmao@qti.qualcomm.com> > --- > drivers/hwtracing/coresight/coresight-sysfs.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c > index 34d2a2d31d00..7df9eb59bf2c 100644 > --- a/drivers/hwtracing/coresight/coresight-sysfs.c > +++ b/drivers/hwtracing/coresight/coresight-sysfs.c > @@ -73,8 +73,10 @@ int coresight_add_sysfs_link(struct coresight_sysfs_link *info) > if (!info->orig || !info->target || > !info->orig_name || !info->target_name) > return -EINVAL; > - if (!info->orig->has_conns_grp || !info->target->has_conns_grp) > + if (!info->orig->has_conns_grp) > return -EINVAL; > + if (!info->target->has_conns_grp) > + return -EPROBE_DEFER; > /* first link orig->target */ > ret = sysfs_add_link_to_group(&info->orig->dev.kobj, > > -- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] coresight: Defer probe when the child dev is not probed 2022-03-01 13:15 ` Mike Leach @ 2022-03-01 13:30 ` Jinlong Mao 2022-03-01 15:03 ` Suzuki K Poulose 0 siblings, 1 reply; 7+ messages in thread From: Jinlong Mao @ 2022-03-01 13:30 UTC (permalink / raw) To: Mike Leach Cc: Suzuki K Poulose, Mathieu Poirier, Leo Yan, Alexander Shishkin, Mao Jinlong, coresight, linux-arm-kernel, linux-kernel, linux-arm-msm, Tingwei Zhang, Yuanfang Zhang, Tao Zhang, Hao Zhang Hi Mike, On 3/1/2022 9:15 PM, Mike Leach wrote: > Hi, > > On Tue, 1 Mar 2022 at 11:42, Jinlong Mao <quic_jinlmao@quicinc.com> wrote: >> On 2/28/2022 10:51 PM, Suzuki K Poulose wrote: >> >> Hi Jinlong >> >> On 28/02/2022 13:31, Mao Jinlong wrote: >> >> From: Mao Jinlong <jinlmao@qti.qualcomm.com> >> >> It is possible that when device probe, its child device is not >> probed. Then it will fail when add sysfs connection for the device. >> Make device defer probe when the child device is not probed. >> >> >> Please could you a bit a more specific on the exact issue ? >> I don't see a problem with probe deferral right now, with >> coresight/next. >> >> For e.g., >> >> root@juno-server:~# lsmod >> Module Size Used by >> coresight 73728 0 >> root@juno-server:~# ls /sys/bus/coresight/devices/ >> root@juno-server:~# modprobe coresight-etm4x >> root@juno-server:~# lsmod >> Module Size Used by >> coresight_etm4x 81920 0 >> coresight 73728 1 coresight_etm4x >> root@juno-server:~# ls /sys/bus/coresight/devices/ >> etm0 etm1 >> >> -- Note etm2-etm5 doesn't appear -- >> >> root@juno-server:~# modprobe coresight-funnel >> root@juno-server:~# lsmod >> Module Size Used by >> coresight_funnel 20480 0 >> coresight_etm4x 81920 0 >> coresight 73728 2 coresight_etm4x,coresight_funnel >> root@juno-server:~# ls /sys/bus/coresight/devices/ >> etm0 etm1 >> >> -- Still don't appear --- >> >> root@juno-server:~# modprobe coresight-replicator >> root@juno-server:~# ls /sys/bus/coresight/devices/ >> etm0 etm1 >> root@juno-server:~# modprobe coresight-tmc >> >> -- At this stage, the devices automatically get probed and appear -- >> root@juno-server:~# ls /sys/bus/coresight/devices/ >> etm0 etm1 etm2 etm3 etm4 etm5 funnel0 funnel1 funnel2 tmc_etf0 tmc_etr0 >> >> >> root@juno-server:~# lsmod >> Module Size Used by >> coresight_tmc 40960 0 >> coresight_replicator 20480 0 >> coresight_funnel 20480 0 >> coresight_etm4x 81920 0 >> coresight 73728 4 coresight_tmc,coresight_etm4x,coresight_replicator,coresight_funnel >> >> So, my question is, what is this patch trying to solve ? >> >> >> Cheers >> Suzuki >> >> Hi Suzuki, >> >> This issue happens when race condition happens. >> The condition is that the device and its child_device's probe happens at the same time. >> >> For example: device0 and its child device device1. >> Both of them are calling coresight_register function. device0 is calling coresight_fixup_device_conns. >> device1 is waiting for device0 to release the coresight_mutex. Because device1's csdev node is allocated, >> coresight_make_links will be called for device0. Then in coresight_add_sysfs_link, has_conns_grp is true >> for device0, but has_conns_grp is false for device1 as has_conns_grp is set to true in coresight_create_conns_sysfs_group . >> The probe of device0 will fail for at this condition. >> >> >> struct coresight_device *coresight_register(struct coresight_desc *desc) >> { >> ......... >> mutex_lock(&coresight_mutex); >> >> ret = coresight_create_conns_sysfs_group(csdev); >> if (!ret) >> ret = coresight_fixup_device_conns(csdev); >> if (!ret) >> ret = coresight_fixup_orphan_conns(csdev); >> if (!ret && cti_assoc_ops && cti_assoc_ops->add) >> cti_assoc_ops->add(csdev); >> >> mutex_unlock(&coresight_mutex); >> >> ......... >> >> } >> >> static int coresight_fixup_device_conns(struct coresight_device *csdev) >> { >> .......... >> conn->child_dev = >> coresight_find_csdev_by_fwnode(conn->child_fwnode); > The issue appears to be a constraint hidden in the lower layers of the code. > Would a better solution not be to alter the code here: > > if (conn->child_dev && conn->child_dev->has_conns_grp) { > ... > } else { > csdev->orphan = true; > } > > which would mean that the connection attempt would drop through to > label the connection as an orphan, to be cleaned up by the child > itself when it runs coresight_fixup_orphan_conns() > > Regards > > Mike Thanks Mike. Your recommended fix looks much better than my fix. Let me try with it and get back to you. Thanks Jinlong Mao > >> if (conn->child_dev) { >> ret = coresight_make_links(csdev, conn, >> >> conn->child_dev); >> >> .......... >> >> } >> >> >> int coresight_add_sysfs_link(struct coresight_sysfs_link *info) >> { >> ................ >> if (!info->orig->has_conns_grp || !info->target->has_conns_grp) >> return -EINVAL; >> >> >> >> The probe fail issue is reproduced with reboot stress test on our internal device. >> >> With the patch, the probe fail issue is not reproduced. >> >> Thanks >> >> Jinlong Mao >> >> >> >> Signed-off-by: Mao Jinlong <jinlmao@qti.qualcomm.com> >> --- >> drivers/hwtracing/coresight/coresight-sysfs.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c >> index 34d2a2d31d00..7df9eb59bf2c 100644 >> --- a/drivers/hwtracing/coresight/coresight-sysfs.c >> +++ b/drivers/hwtracing/coresight/coresight-sysfs.c >> @@ -73,8 +73,10 @@ int coresight_add_sysfs_link(struct coresight_sysfs_link *info) >> if (!info->orig || !info->target || >> !info->orig_name || !info->target_name) >> return -EINVAL; >> - if (!info->orig->has_conns_grp || !info->target->has_conns_grp) >> + if (!info->orig->has_conns_grp) >> return -EINVAL; >> + if (!info->target->has_conns_grp) >> + return -EPROBE_DEFER; >> /* first link orig->target */ >> ret = sysfs_add_link_to_group(&info->orig->dev.kobj, >> >> > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] coresight: Defer probe when the child dev is not probed 2022-03-01 13:30 ` Jinlong Mao @ 2022-03-01 15:03 ` Suzuki K Poulose 2022-03-02 2:29 ` Jinlong Mao 0 siblings, 1 reply; 7+ messages in thread From: Suzuki K Poulose @ 2022-03-01 15:03 UTC (permalink / raw) To: Jinlong Mao, Mike Leach Cc: Mathieu Poirier, Leo Yan, Alexander Shishkin, Mao Jinlong, coresight, linux-arm-kernel, linux-kernel, linux-arm-msm, Tingwei Zhang, Yuanfang Zhang, Tao Zhang, Hao Zhang Hi On 01/03/2022 13:30, Jinlong Mao wrote: > Hi Mike, > > On 3/1/2022 9:15 PM, Mike Leach wrote: >> Hi, >> >> On Tue, 1 Mar 2022 at 11:42, Jinlong Mao <quic_jinlmao@quicinc.com> >> wrote: >>> On 2/28/2022 10:51 PM, Suzuki K Poulose wrote: >>> ... >>> >>> Hi Suzuki, >>> >>> This issue happens when race condition happens. >>> The condition is that the device and its child_device's probe happens >>> at the same time. >>> >>> For example: device0 and its child device device1. >>> Both of them are calling coresight_register function. device0 is >>> calling coresight_fixup_device_conns. >>> device1 is waiting for device0 to release the coresight_mutex. >>> Because device1's csdev node is allocated, >>> coresight_make_links will be called for device0. Then in >>> coresight_add_sysfs_link, has_conns_grp is true >>> for device0, but has_conns_grp is false for device1 as has_conns_grp >>> is set to true in coresight_create_conns_sysfs_group . >>> The probe of device0 will fail for at this condition. >>> >>> >>> struct coresight_device *coresight_register(struct coresight_desc *desc) >>> { >>> ......... >>> mutex_lock(&coresight_mutex); >>> >>> ret = coresight_create_conns_sysfs_group(csdev); >>> if (!ret) >>> ret = coresight_fixup_device_conns(csdev); >>> if (!ret) >>> ret = coresight_fixup_orphan_conns(csdev); >>> if (!ret && cti_assoc_ops && cti_assoc_ops->add) >>> cti_assoc_ops->add(csdev); >>> >>> mutex_unlock(&coresight_mutex); >>> >>> ......... >>> >>> } >>> >>> static int coresight_fixup_device_conns(struct coresight_device *csdev) >>> { >>> .......... >>> conn->child_dev = >>> coresight_find_csdev_by_fwnode(conn->child_fwnode); >> The issue appears to be a constraint hidden in the lower layers of the >> code. >> Would a better solution not be to alter the code here: >> >> if (conn->child_dev && conn->child_dev->has_conns_grp) { >> ... >> } else { >> csdev->orphan = true; >> } >> >> which would mean that the connection attempt would drop through to >> label the connection as an orphan, to be cleaned up by the child >> itself when it runs coresight_fixup_orphan_conns() >> Tnanks Mike, I think that is a good solution. Alternatively, we could make sure that device_register() and the fixup following that are atomic. i.e. mutex_lock() device_register() fixup_connections() create_sysfs() mutex_unlock(); The fix may be a bit invasive than Mike's proposal, but it makes sure we don't end up with half baked device on the coresight-bus. Suzuki ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] coresight: Defer probe when the child dev is not probed 2022-03-01 15:03 ` Suzuki K Poulose @ 2022-03-02 2:29 ` Jinlong Mao 2022-03-02 8:05 ` Jinlong Mao 0 siblings, 1 reply; 7+ messages in thread From: Jinlong Mao @ 2022-03-02 2:29 UTC (permalink / raw) To: Suzuki K Poulose, Mike Leach Cc: Mathieu Poirier, Leo Yan, Alexander Shishkin, Mao Jinlong, coresight, linux-arm-kernel, linux-kernel, linux-arm-msm, Tingwei Zhang, Yuanfang Zhang, Tao Zhang, Hao Zhang On 3/1/2022 11:03 PM, Suzuki K Poulose wrote: > Hi > > On 01/03/2022 13:30, Jinlong Mao wrote: >> Hi Mike, >> >> On 3/1/2022 9:15 PM, Mike Leach wrote: >>> Hi, >>> >>> On Tue, 1 Mar 2022 at 11:42, Jinlong Mao <quic_jinlmao@quicinc.com> >>> wrote: >>>> On 2/28/2022 10:51 PM, Suzuki K Poulose wrote: >>>> > > ... > >>>> >>>> Hi Suzuki, >>>> >>>> This issue happens when race condition happens. >>>> The condition is that the device and its child_device's probe >>>> happens at the same time. >>>> >>>> For example: device0 and its child device device1. >>>> Both of them are calling coresight_register function. device0 is >>>> calling coresight_fixup_device_conns. >>>> device1 is waiting for device0 to release the coresight_mutex. >>>> Because device1's csdev node is allocated, >>>> coresight_make_links will be called for device0. Then in >>>> coresight_add_sysfs_link, has_conns_grp is true >>>> for device0, but has_conns_grp is false for device1 as >>>> has_conns_grp is set to true in coresight_create_conns_sysfs_group . >>>> The probe of device0 will fail for at this condition. >>>> >>>> >>>> struct coresight_device *coresight_register(struct coresight_desc >>>> *desc) >>>> { >>>> ......... >>>> mutex_lock(&coresight_mutex); >>>> >>>> ret = coresight_create_conns_sysfs_group(csdev); >>>> if (!ret) >>>> ret = coresight_fixup_device_conns(csdev); >>>> if (!ret) >>>> ret = coresight_fixup_orphan_conns(csdev); >>>> if (!ret && cti_assoc_ops && cti_assoc_ops->add) >>>> cti_assoc_ops->add(csdev); >>>> >>>> mutex_unlock(&coresight_mutex); >>>> >>>> ......... >>>> >>>> } >>>> >>>> static int coresight_fixup_device_conns(struct coresight_device >>>> *csdev) >>>> { >>>> .......... >>>> conn->child_dev = >>>> coresight_find_csdev_by_fwnode(conn->child_fwnode); >>> The issue appears to be a constraint hidden in the lower layers of >>> the code. >>> Would a better solution not be to alter the code here: >>> >>> if (conn->child_dev && conn->child_dev->has_conns_grp) { >>> ... >>> } else { >>> csdev->orphan = true; >>> } >>> >>> which would mean that the connection attempt would drop through to >>> label the connection as an orphan, to be cleaned up by the child >>> itself when it runs coresight_fixup_orphan_conns() >>> > > Tnanks Mike, I think that is a good solution. Alternatively, we > could make sure that device_register() and the fixup following > that are atomic. > > i.e. > > mutex_lock() > > device_register() > fixup_connections() > create_sysfs() > > mutex_unlock(); > > The fix may be a bit invasive than Mike's proposal, but it makes > sure we don't end up with half baked device on the coresight-bus. > > Suzuki Thanks Mike & Suzuki. I will combine your proposals and make the changes. I will get back to you after the test. Thanks Jinlong Mao ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] coresight: Defer probe when the child dev is not probed 2022-03-02 2:29 ` Jinlong Mao @ 2022-03-02 8:05 ` Jinlong Mao 0 siblings, 0 replies; 7+ messages in thread From: Jinlong Mao @ 2022-03-02 8:05 UTC (permalink / raw) To: Suzuki K Poulose, Mike Leach Cc: Mathieu Poirier, Leo Yan, Alexander Shishkin, Mao Jinlong, coresight, linux-arm-kernel, linux-kernel, linux-arm-msm, Tingwei Zhang, Yuanfang Zhang, Tao Zhang, Hao Zhang On 3/2/2022 10:29 AM, Jinlong Mao wrote: > > On 3/1/2022 11:03 PM, Suzuki K Poulose wrote: >> Hi >> >> On 01/03/2022 13:30, Jinlong Mao wrote: >>> Hi Mike, >>> >>> On 3/1/2022 9:15 PM, Mike Leach wrote: >>>> Hi, >>>> >>>> On Tue, 1 Mar 2022 at 11:42, Jinlong Mao <quic_jinlmao@quicinc.com> >>>> wrote: >>>>> On 2/28/2022 10:51 PM, Suzuki K Poulose wrote: >>>>> >> >> ... >> >>>>> >>>>> Hi Suzuki, >>>>> >>>>> This issue happens when race condition happens. >>>>> The condition is that the device and its child_device's probe >>>>> happens at the same time. >>>>> >>>>> For example: device0 and its child device device1. >>>>> Both of them are calling coresight_register function. device0 is >>>>> calling coresight_fixup_device_conns. >>>>> device1 is waiting for device0 to release the coresight_mutex. >>>>> Because device1's csdev node is allocated, >>>>> coresight_make_links will be called for device0. Then in >>>>> coresight_add_sysfs_link, has_conns_grp is true >>>>> for device0, but has_conns_grp is false for device1 as >>>>> has_conns_grp is set to true in coresight_create_conns_sysfs_group . >>>>> The probe of device0 will fail for at this condition. >>>>> >>>>> >>>>> struct coresight_device *coresight_register(struct coresight_desc >>>>> *desc) >>>>> { >>>>> ......... >>>>> mutex_lock(&coresight_mutex); >>>>> >>>>> ret = coresight_create_conns_sysfs_group(csdev); >>>>> if (!ret) >>>>> ret = coresight_fixup_device_conns(csdev); >>>>> if (!ret) >>>>> ret = coresight_fixup_orphan_conns(csdev); >>>>> if (!ret && cti_assoc_ops && cti_assoc_ops->add) >>>>> cti_assoc_ops->add(csdev); >>>>> >>>>> mutex_unlock(&coresight_mutex); >>>>> >>>>> ......... >>>>> >>>>> } >>>>> >>>>> static int coresight_fixup_device_conns(struct coresight_device >>>>> *csdev) >>>>> { >>>>> .......... >>>>> conn->child_dev = >>>>> coresight_find_csdev_by_fwnode(conn->child_fwnode); >>>> The issue appears to be a constraint hidden in the lower layers of >>>> the code. >>>> Would a better solution not be to alter the code here: >>>> >>>> if (conn->child_dev && conn->child_dev->has_conns_grp) { >>>> ... >>>> } else { >>>> csdev->orphan = true; >>>> } >>>> >>>> which would mean that the connection attempt would drop through to >>>> label the connection as an orphan, to be cleaned up by the child >>>> itself when it runs coresight_fixup_orphan_conns() >>>> >> >> Tnanks Mike, I think that is a good solution. Alternatively, we >> could make sure that device_register() and the fixup following >> that are atomic. >> >> i.e. >> >> mutex_lock() >> >> device_register() >> fixup_connections() >> create_sysfs() >> >> mutex_unlock(); >> >> The fix may be a bit invasive than Mike's proposal, but it makes >> sure we don't end up with half baked device on the coresight-bus. >> >> Suzuki > > Thanks Mike & Suzuki. > > I will combine your proposals and make the changes. > > I will get back to you after the test. Hi Mike & Suzuki, Issue is fixed with your proposal. I submit a new patch "coresight: core: Fix coresight device probe failure issue". Please help to review. Thanks Jinlong Mao > > > Thanks > Jinlong Mao > ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2022-03-02 8:05 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2022-02-28 13:31 [PATCH] coresight: Defer probe when the child dev is not probed Mao Jinlong
2022-02-28 14:51 ` Suzuki K Poulose
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2022-03-01 13:15 ` Mike Leach
2022-03-01 13:30 ` Jinlong Mao
2022-03-01 15:03 ` Suzuki K Poulose
2022-03-02 2:29 ` Jinlong Mao
2022-03-02 8:05 ` Jinlong Mao
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