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![]() When we have an SHPC-capable bridge with a second SHPC-capable bridge below it, pushing the upstream bridge's attention button causes a deadlock. The deadlock happens because we use the shpchp_wq workqueue to run shpchp_pushbutton_thread(), which uses shpchp_disable_slot() to remove devices below the upstream bridge. When we remove the downstream bridge, we call shpc_remove(), the shpchp driver's .remove() method. That calls flush_workqueue(shpchp_wq), which deadlocks because the shpchp_pushbutton_thread() work item is still running. This patch avoids the deadlock by creating a workqueue for every slot and removing the single shared workqueue. Here's the call path that leads to the deadlock: shpchp_queue_pushbutton_work queue_work(shpchp_wq) # shpchp_pushbutton_thread ... shpchp_pushbutton_thread shpchp_disable_slot remove_board shpchp_unconfigure_device pci_stop_and_remove_bus_device ... shpc_remove # shpchp driver .remove method hpc_release_ctlr cleanup_slots flush_workqueue(shpchp_wq) This change is based on code inspection, since we don't have hardware with this topology. Based-on-patch-by: Yijing Wang <wangyijing@huawei.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> CC: stable@vger.kernel.org |
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.. | ||
acpi_pcihp.c | ||
acpiphp.h | ||
acpiphp_core.c | ||
acpiphp_glue.c | ||
acpiphp_ibm.c | ||
cpci_hotplug.h | ||
cpci_hotplug_core.c | ||
cpci_hotplug_pci.c | ||
cpcihp_generic.c | ||
cpcihp_zt5550.c | ||
cpcihp_zt5550.h | ||
cpqphp.h | ||
cpqphp_core.c | ||
cpqphp_ctrl.c | ||
cpqphp_nvram.c | ||
cpqphp_nvram.h | ||
cpqphp_pci.c | ||
cpqphp_sysfs.c | ||
ibmphp.h | ||
ibmphp_core.c | ||
ibmphp_ebda.c | ||
ibmphp_hpc.c | ||
ibmphp_pci.c | ||
ibmphp_res.c | ||
Kconfig | ||
Makefile | ||
pci_hotplug_core.c | ||
pciehp.h | ||
pciehp_acpi.c | ||
pciehp_core.c | ||
pciehp_ctrl.c | ||
pciehp_hpc.c | ||
pciehp_pci.c | ||
pcihp_skeleton.c | ||
pcihp_slot.c | ||
rpadlpar.h | ||
rpadlpar_core.c | ||
rpadlpar_sysfs.c | ||
rpaphp.h | ||
rpaphp_core.c | ||
rpaphp_pci.c | ||
rpaphp_slot.c | ||
s390_pci_hpc.c | ||
sgi_hotplug.c | ||
shpchp.h | ||
shpchp_core.c | ||
shpchp_ctrl.c | ||
shpchp_hpc.c | ||
shpchp_pci.c | ||
shpchp_sysfs.c |