Messages in this thread | | | Date | Wed, 2 Mar 2022 16:05:05 +0800 | Subject | Re: [PATCH] coresight: Defer probe when the child dev is not probed | From | Jinlong Mao <> |
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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 >
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