[PATCH v2] Bugfix: powerpc/eeh: Wrong place to call pci_get_slot()

[Gavin Shan]

On Mon, Jul 14, 2014 at 10:33:48PM -0400, Mike Qiu wrote:
>pci_get_slot() is called with hold of PCI bus semaphore and it's not
>safe to be called in interrupt context. However, we possibly checks
>EEH error and calls the function in interrupt context. To avoid using
>pci_get_slot(), we turn into device tree for fetching location code.
>Otherwise, we might run into WARN_ON() as following messages indicate:
>
> WARNING: at drivers/pci/search.c:223
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.16.0-rc3+ #72
> task: c000000001367af0 ti: c000000001444000 task.ti: c000000001444000
> NIP: c000000000497b70 LR: c000000000037530 CTR: 000000003003d114
> REGS: c000000001446fa0 TRAP: 0700   Not tainted  (3.16.0-rc3+)
> MSR: 9000000000029032 <SF,HV,EE,ME,IR,DR,RI>  CR: 48002422  XER: 20000000
> CFAR: c00000000003752c SOFTE: 0
>   :
> NIP [c000000000497b70] .pci_get_slot+0x40/0x110
> LR [c000000000037530] .eeh_pe_loc_get+0x150/0x190
> Call Trace:
>   .of_get_property+0x30/0x60 (unreliable)
>   .eeh_pe_loc_get+0x150/0x190
>   .eeh_dev_check_failure+0x1b4/0x550
>   .eeh_check_failure+0x90/0xf0
>   .lpfc_sli_check_eratt+0x504/0x7c0 [lpfc]
>   .lpfc_poll_eratt+0x64/0x100 [lpfc]
>   .call_timer_fn+0x64/0x190
>   .run_timer_softirq+0x2cc/0x3e0
>
>Signed-off-by: Mike Qiu <qiudayu at linux.vnet.ibm.com>
>---
> Changelog[v2]:
>	Check the child device_node of root bus for root port
>	directly instead of search pdev from device-tree and
>	then translate it to device-node
>

I run into following warning with your patch. Please test the attached
one. If no problem found, send that one please.

arch/powerpc/kernel/eeh_pe.c: In function 'eeh_pe_loc_get':
arch/powerpc/kernel/eeh_pe.c:806:18: warning: unused variable 'pdev'

Thanks,
Gavin

> arch/powerpc/kernel/eeh_pe.c | 24 ++++++------------------
> 1 file changed, 6 insertions(+), 18 deletions(-)
>
>diff --git a/arch/powerpc/kernel/eeh_pe.c b/arch/powerpc/kernel/eeh_pe.c
>index fbd01eb..f96c10f 100644
>--- a/arch/powerpc/kernel/eeh_pe.c
>+++ b/arch/powerpc/kernel/eeh_pe.c
>@@ -802,7 +802,6 @@ void eeh_pe_restore_bars(struct eeh_pe *pe)
>  */
> const char *eeh_pe_loc_get(struct eeh_pe *pe)
> {
>-	struct pci_controller *hose;
> 	struct pci_bus *bus = eeh_pe_bus_get(pe);
> 	struct pci_dev *pdev;
> 	struct device_node *dn;
>@@ -811,29 +810,20 @@ const char *eeh_pe_loc_get(struct eeh_pe *pe)
> 	if (!bus)
> 		return "N/A";
>
>+	dn = pci_bus_to_OF_node(bus);
> 	/* PHB PE or root PE ? */
>-	if (pci_is_root_bus(bus)) {
>-		hose = pci_bus_to_host(bus);
>-		loc = of_get_property(hose->dn,
>-				"ibm,loc-code", NULL);
>+	if (dn && pci_is_root_bus(bus)) {
>+		loc = of_get_property(dn, "ibm,loc-code", NULL);
> 		if (loc)
> 			return loc;
>-		loc = of_get_property(hose->dn,
>-				"ibm,io-base-loc-code", NULL);
>+		loc = of_get_property(dn, "ibm,io-base-loc-code", NULL);
> 		if (loc)
> 			return loc;
>
>-		pdev = pci_get_slot(bus, 0x0);
>-	} else {
>-		pdev = bus->self;
>-	}
>-
>-	if (!pdev) {
>-		loc = "N/A";
>-		goto out;
>+		/* Check the root port */
>+		dn = dn->child;
> 	}
>
>-	dn = pci_device_to_OF_node(pdev);
> 	if (!dn) {
> 		loc = "N/A";
> 		goto out;
>@@ -846,8 +836,6 @@ const char *eeh_pe_loc_get(struct eeh_pe *pe)
> 		loc = "N/A";
>
> out:
>-	if (pci_is_root_bus(bus) && pdev)
>-		pci_dev_put(pdev);
> 	return loc;
> }
>
>-- 
>1.8.1.4
>
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