[PATCH v2 0/3] PCI: Data corruption happening due to race condition

[PATCH v2 0/3] PCI: Data corruption happening due to race condition

[Hari Vyas]

Changes in v2:
	To avoid race condition while updating is_added and is_busmaster
	bits, is_added is moved to a private flag variable.
	is_added updation is handled in atomic manner also.

Hari Vyas (3):
  PCI: Data corruption happening due to race condition
  PCI: use new pci function to get device addition state
  PCI: Hotplug: use new pci function to get device addition state

 arch/powerpc/kernel/pci-common.c          |  4 +++-
 arch/powerpc/platforms/powernv/pci-ioda.c |  3 ++-
 arch/powerpc/platforms/pseries/setup.c    |  3 ++-
 drivers/pci/bus.c                         |  6 +++---
 drivers/pci/hotplug/acpiphp_glue.c        |  2 +-
 drivers/pci/pci.c                         |  1 +
 drivers/pci/pci.h                         | 18 ++++++++++++++++++
 drivers/pci/probe.c                       |  4 ++--
 drivers/pci/remove.c                      |  5 +++--
 include/linux/pci.h                       |  1 -
 10 files changed, 35 insertions(+), 12 deletions(-)

-- 
1.9.1

[PATCH v2 1/3] PCI: Data corruption happening due to race condition

[Hari Vyas]

When a pci device is detected, a variable is_added is set to
1 in pci device structure and proc, sys entries are created.

When a pci device is removed, first is_added is checked for one
and then device is detached with clearing of proc and sys
entries and at end, is_added is set to 0.

is_added and is_busmaster are bit fields in pci_dev structure
sharing same memory location.

A strange issue was observed with multiple times removal and
rescan of a pcie nvme device using sysfs commands where is_added
flag was observed as zero instead of one while removing device
and proc,sys entries are not cleared.  This causes issue in
later device addition with warning message "proc_dir_entry"
already registered.

Debugging revealed a race condition between pcie core driver
enabling is_added bit(pci_bus_add_device()) and nvme driver
reset work-queue enabling is_busmaster bit (by pci_set_master()).
As both fields are not handled in atomic manner and that clears
is_added bit.

Fix moves device addition is_added bit to separate private flag
variable and use different atomic functions to set, clear and
retrieve device addition state. As is_added shares different
memory location so race condition is avoided.

Signed-off-by: Hari Vyas <hari.vyas@broadcom.com>
---
 drivers/pci/bus.c    |  6 +++---
 drivers/pci/pci.c    |  1 +
 drivers/pci/pci.h    | 18 ++++++++++++++++++
 drivers/pci/probe.c  |  4 ++--
 drivers/pci/remove.c |  5 +++--
 include/linux/pci.h  |  1 -
 6 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 35b7fc8..8674019 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -330,7 +330,7 @@ void pci_bus_add_device(struct pci_dev *dev)
 		return;
 	}
 
-	dev->is_added = 1;
+	pci_dev_set_added(dev, NULL);
 }
 EXPORT_SYMBOL_GPL(pci_bus_add_device);
 
@@ -347,14 +347,14 @@ void pci_bus_add_devices(const struct pci_bus *bus)
 
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		/* Skip already-added devices */
-		if (dev->is_added)
+		if (pci_dev_is_added(dev))
 			continue;
 		pci_bus_add_device(dev);
 	}
 
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		/* Skip if device attach failed */
-		if (!dev->is_added)
+		if (!pci_dev_is_added(dev))
 			continue;
 		child = dev->subordinate;
 		if (child)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 97acba7..baefd55 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3675,6 +3675,7 @@ static void __pci_set_master(struct pci_dev *dev, bool enable)
 			enable ? "enabling" : "disabling");
 		pci_write_config_word(dev, PCI_COMMAND, cmd);
 	}
+
 	dev->is_busmaster = enable;
 }
 
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index c358e7a0..c924a4c 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -288,6 +288,7 @@ struct pci_sriov {
 
 /* pci_dev priv_flags */
 #define PCI_DEV_DISCONNECTED 0
+#define PCI_DEV_ADDED 1
 
 static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
 {
@@ -300,6 +301,23 @@ static inline bool pci_dev_is_disconnected(const struct pci_dev *dev)
 	return test_bit(PCI_DEV_DISCONNECTED, &dev->priv_flags);
 }
 
+static inline int pci_dev_set_added(struct pci_dev *dev, void *unused)
+{
+	set_bit(PCI_DEV_ADDED, &dev->priv_flags);
+	return 0;
+}
+
+static inline int pci_dev_clear_added(struct pci_dev *dev, void *unused)
+{
+	clear_bit(PCI_DEV_ADDED, &dev->priv_flags);
+	return 0;
+}
+
+static inline bool pci_dev_is_added(const struct pci_dev *dev)
+{
+	return test_bit(PCI_DEV_ADDED, &dev->priv_flags);
+}
+
 #ifdef CONFIG_PCI_ATS
 void pci_restore_ats_state(struct pci_dev *dev);
 #else
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ac876e3..611adcd 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2433,13 +2433,13 @@ int pci_scan_slot(struct pci_bus *bus, int devfn)
 	dev = pci_scan_single_device(bus, devfn);
 	if (!dev)
 		return 0;
-	if (!dev->is_added)
+	if (!pci_dev_is_added(dev))
 		nr++;
 
 	for (fn = next_fn(bus, dev, 0); fn > 0; fn = next_fn(bus, dev, fn)) {
 		dev = pci_scan_single_device(bus, devfn + fn);
 		if (dev) {
-			if (!dev->is_added)
+			if (!pci_dev_is_added(dev))
 				nr++;
 			dev->multifunction = 1;
 		}
diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index 6f072ea..a272cdc 100644
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -19,11 +19,12 @@ static void pci_stop_dev(struct pci_dev *dev)
 {
 	pci_pme_active(dev, false);
 
-	if (dev->is_added) {
+	if (pci_dev_is_added(dev)) {
 		device_release_driver(&dev->dev);
 		pci_proc_detach_device(dev);
 		pci_remove_sysfs_dev_files(dev);
-		dev->is_added = 0;
+
+		pci_dev_clear_added(dev, NULL);
 	}
 
 	if (dev->bus->self)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 340029b..506125b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -368,7 +368,6 @@ struct pci_dev {
 	unsigned int	transparent:1;		/* Subtractive decode bridge */
 	unsigned int	multifunction:1;	/* Multi-function device */
 
-	unsigned int	is_added:1;
 	unsigned int	is_busmaster:1;		/* Is busmaster */
 	unsigned int	no_msi:1;		/* May not use MSI */
 	unsigned int	no_64bit_msi:1; 	/* May only use 32-bit MSIs */
-- 
1.9.1

[PATCH v2 2/3] PCI: use new pci function to get device addition state

[Hari Vyas]

Due to one race condition happening while updating pci
device addition and master status bits in a particular
scenario, device addition state is moved to a independent
private flag variable.

This change uses newly proposed pci_dev_is_added() function
to retrieve device addition state.

Signed-off-by: Hari Vyas <hari.vyas@broadcom.com>
---
 arch/powerpc/kernel/pci-common.c          | 4 +++-
 arch/powerpc/platforms/powernv/pci-ioda.c | 3 ++-
 arch/powerpc/platforms/pseries/setup.c    | 3 ++-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index fe9733f..471aac3 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -42,6 +42,8 @@
 #include <asm/ppc-pci.h>
 #include <asm/eeh.h>
 
+#include "../../../drivers/pci/pci.h"
+
 /* hose_spinlock protects accesses to the the phb_bitmap. */
 static DEFINE_SPINLOCK(hose_spinlock);
 LIST_HEAD(hose_list);
@@ -1014,7 +1016,7 @@ void pcibios_setup_bus_devices(struct pci_bus *bus)
 		/* Cardbus can call us to add new devices to a bus, so ignore
 		 * those who are already fully discovered
 		 */
-		if (dev->is_added)
+		if (pci_dev_is_added(dev))
 			continue;
 
 		pcibios_setup_device(dev);
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 5bd0eb6..70b2e1e 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -46,6 +46,7 @@
 
 #include "powernv.h"
 #include "pci.h"
+#include "../../../../drivers/pci/pci.h"
 
 #define PNV_IODA1_M64_NUM	16	/* Number of M64 BARs	*/
 #define PNV_IODA1_M64_SEGS	8	/* Segments per M64 BAR	*/
@@ -3138,7 +3139,7 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
 	struct pci_dn *pdn;
 	int mul, total_vfs;
 
-	if (!pdev->is_physfn || pdev->is_added)
+	if (!pdev->is_physfn || pci_dev_is_added(pdev))
 		return;
 
 	pdn = pci_get_pdn(pdev);
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 139f0af..8a4868a 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -71,6 +71,7 @@
 #include <asm/security_features.h>
 
 #include "pseries.h"
+#include "../../../../drivers/pci/pci.h"
 
 int CMO_PrPSP = -1;
 int CMO_SecPSP = -1;
@@ -664,7 +665,7 @@ static void pseries_pci_fixup_iov_resources(struct pci_dev *pdev)
 	const int *indexes;
 	struct device_node *dn = pci_device_to_OF_node(pdev);
 
-	if (!pdev->is_physfn || pdev->is_added)
+	if (!pdev->is_physfn || pci_dev_is_added(pdev))
 		return;
 	/*Firmware must support open sriov otherwise dont configure*/
 	indexes = of_get_property(dn, "ibm,open-sriov-vf-bar-info", NULL);
-- 
1.9.1

[PATCH v2 3/3] PCI: Hotplug: use new pci function to get device addition state

[Hari Vyas]

Due to one race condition happening while updating pci
device addition and master status bits in a particular
scenario, device addition state is moved to a independent
private flag variable.

This change uses newly proposed pci_dev_is_added() function
to retrieve device addition state.

Signed-off-by: Hari Vyas <hari.vyas@broadcom.com>
---
 drivers/pci/hotplug/acpiphp_glue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index 3a17b29..ef0b1b6 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -509,7 +509,7 @@ static void enable_slot(struct acpiphp_slot *slot)
 
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		/* Assume that newly added devices are powered on already. */
-		if (!dev->is_added)
+		if (!pci_dev_is_added(dev))
 			dev->current_state = PCI_D0;
 	}
 
-- 
1.9.1

Re: [PATCH v2 1/3] PCI: Data corruption happening due to race condition

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 7095 bytes --]

Hi Hari,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on pci/next]
[also build test ERROR on v4.18-rc2 next-20180629]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Hari-Vyas/PCI-Data-corruption-happening-due-to-race-condition/20180629-203647
base:   https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git next
config: x86_64-randconfig-x005-201825 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

Note: the linux-review/Hari-Vyas/PCI-Data-corruption-happening-due-to-race-condition/20180629-203647 HEAD 75ee48282af54fe77cb0ac092623577327440033 builds fine.
      It only hurts bisectibility.

All errors (new ones prefixed by >>):

   drivers/pci/hotplug/acpiphp_glue.c: In function 'enable_slot':
>> drivers/pci/hotplug/acpiphp_glue.c:512:13: error: 'struct pci_dev' has no member named 'is_added'; did you mean 'is_managed'?
      if (!dev->is_added)
                ^~~~~~~~
                is_managed

vim +512 drivers/pci/hotplug/acpiphp_glue.c

84c8b58ed3 Mika Westerberg   2018-05-29  456  
^1da177e4c Linus Torvalds    2005-04-16  457  /**
a1d0abcea8 Rafael J. Wysocki 2013-07-13  458   * enable_slot - enable, configure a slot
^1da177e4c Linus Torvalds    2005-04-16  459   * @slot: slot to be enabled
^1da177e4c Linus Torvalds    2005-04-16  460   *
^1da177e4c Linus Torvalds    2005-04-16  461   * This function should be called per *physical slot*,
^1da177e4c Linus Torvalds    2005-04-16  462   * not per each slot object in ACPI namespace.
^1da177e4c Linus Torvalds    2005-04-16  463   */
10874f5a00 Bjorn Helgaas     2014-04-14  464  static void enable_slot(struct acpiphp_slot *slot)
^1da177e4c Linus Torvalds    2005-04-16  465  {
^1da177e4c Linus Torvalds    2005-04-16  466  	struct pci_dev *dev;
bda46dbb66 Rafael J. Wysocki 2013-07-13  467  	struct pci_bus *bus = slot->bus;
^1da177e4c Linus Torvalds    2005-04-16  468  	struct acpiphp_func *func;
84c8b58ed3 Mika Westerberg   2018-05-29  469  
84c8b58ed3 Mika Westerberg   2018-05-29  470  	if (bus->self && hotplug_is_native(bus->self)) {
84c8b58ed3 Mika Westerberg   2018-05-29  471  		/*
84c8b58ed3 Mika Westerberg   2018-05-29  472  		 * If native hotplug is used, it will take care of hotplug
84c8b58ed3 Mika Westerberg   2018-05-29  473  		 * slot management and resource allocation for hotplug
84c8b58ed3 Mika Westerberg   2018-05-29  474  		 * bridges. However, ACPI hotplug may still be used for
84c8b58ed3 Mika Westerberg   2018-05-29  475  		 * non-hotplug bridges to bring in additional devices such
84c8b58ed3 Mika Westerberg   2018-05-29  476  		 * as a Thunderbolt host controller.
84c8b58ed3 Mika Westerberg   2018-05-29  477  		 */
84c8b58ed3 Mika Westerberg   2018-05-29  478  		for_each_pci_bridge(dev, bus) {
84c8b58ed3 Mika Westerberg   2018-05-29  479  			if (PCI_SLOT(dev->devfn) == slot->device)
84c8b58ed3 Mika Westerberg   2018-05-29  480  				acpiphp_native_scan_bridge(dev);
84c8b58ed3 Mika Westerberg   2018-05-29  481  		}
84c8b58ed3 Mika Westerberg   2018-05-29  482  		pci_assign_unassigned_bridge_resources(bus->self);
84c8b58ed3 Mika Westerberg   2018-05-29  483  	} else {
d66ecb7220 Jiang Liu         2013-06-23  484  		LIST_HEAD(add_list);
84c8b58ed3 Mika Westerberg   2018-05-29  485  		int max, pass;
^1da177e4c Linus Torvalds    2005-04-16  486  
ab1225901d Mika Westerberg   2013-10-30  487  		acpiphp_rescan_slot(slot);
15a1ae7487 Kristen Accardi   2006-02-23  488  		max = acpiphp_max_busnr(bus);
42f49a6ae5 Rajesh Shah       2005-04-28  489  		for (pass = 0; pass < 2; pass++) {
24a0c654d7 Andy Shevchenko   2017-10-20  490  			for_each_pci_bridge(dev, bus) {
42f49a6ae5 Rajesh Shah       2005-04-28  491  				if (PCI_SLOT(dev->devfn) != slot->device)
42f49a6ae5 Rajesh Shah       2005-04-28  492  					continue;
a1d0abcea8 Rafael J. Wysocki 2013-07-13  493  
42f49a6ae5 Rajesh Shah       2005-04-28  494  				max = pci_scan_bridge(bus, dev, max, pass);
1f96a965e3 Yinghai Lu        2013-01-21  495  				if (pass && dev->subordinate) {
1f96a965e3 Yinghai Lu        2013-01-21  496  					check_hotplug_bridge(slot, dev);
d66ecb7220 Jiang Liu         2013-06-23  497  					pcibios_resource_survey_bus(dev->subordinate);
84c8b58ed3 Mika Westerberg   2018-05-29  498  					__pci_bus_size_bridges(dev->subordinate,
84c8b58ed3 Mika Westerberg   2018-05-29  499  							       &add_list);
c64b5eead9 Kristen Accardi   2005-12-14  500  				}
42f49a6ae5 Rajesh Shah       2005-04-28  501  			}
1f96a965e3 Yinghai Lu        2013-01-21  502  		}
d66ecb7220 Jiang Liu         2013-06-23  503  		__pci_bus_assign_resources(bus, &add_list, NULL);
84c8b58ed3 Mika Westerberg   2018-05-29  504  	}
2dc41281b1 Rafael J. Wysocki 2013-09-06  505  
8e5dce3522 Kristen Accardi   2005-10-18  506  	acpiphp_sanitize_bus(bus);
81ee57326c Bjorn Helgaas     2014-08-28  507  	pcie_bus_configure_settings(bus);
d060705091 Shaohua Li        2010-02-25  508  	acpiphp_set_acpi_region(slot);
69643e4829 Ian Campbell      2011-05-11  509  
69643e4829 Ian Campbell      2011-05-11  510  	list_for_each_entry(dev, &bus->devices, bus_list) {
69643e4829 Ian Campbell      2011-05-11  511  		/* Assume that newly added devices are powered on already. */
69643e4829 Ian Campbell      2011-05-11 @512  		if (!dev->is_added)
69643e4829 Ian Campbell      2011-05-11  513  			dev->current_state = PCI_D0;
69643e4829 Ian Campbell      2011-05-11  514  	}
69643e4829 Ian Campbell      2011-05-11  515  
42f49a6ae5 Rajesh Shah       2005-04-28  516  	pci_bus_add_devices(bus);
42f49a6ae5 Rajesh Shah       2005-04-28  517  
f382a086f3 Amos Kong         2011-11-25  518  	slot->flags |= SLOT_ENABLED;
58c08628c4 Alex Chiang       2009-10-26  519  	list_for_each_entry(func, &slot->funcs, sibling) {
9d911d7903 Alex Chiang       2009-05-21  520  		dev = pci_get_slot(bus, PCI_DEVFN(slot->device,
^1da177e4c Linus Torvalds    2005-04-16  521  						  func->function));
f382a086f3 Amos Kong         2011-11-25  522  		if (!dev) {
f382a086f3 Amos Kong         2011-11-25  523  			/* Do not set SLOT_ENABLED flag if some funcs
f382a086f3 Amos Kong         2011-11-25  524  			   are not added. */
9337a49362 Mika Westerberg   2018-05-24  525  			slot->flags &= ~SLOT_ENABLED;
551bcb75b3 MUNEDA Takahiro   2006-03-22  526  			continue;
f382a086f3 Amos Kong         2011-11-25  527  		}
^1da177e4c Linus Torvalds    2005-04-16  528  	}
^1da177e4c Linus Torvalds    2005-04-16  529  }
^1da177e4c Linus Torvalds    2005-04-16  530  

:::::: The code at line 512 was first introduced by commit
:::::: 69643e4829c5cd13bafe44a6b9f3eb2086e0f618 PCI hotplug: acpiphp: assume device is in state D0 after powering on a slot.

:::::: TO: Ian Campbell <ian.campbell@citrix.com>
:::::: CC: Jesse Barnes <jbarnes@virtuousgeek.org>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 29890 bytes --]

Re: [PATCH v2 1/3] PCI: Data corruption happening due to race condition

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 3192 bytes --]

Hi Hari,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on pci/next]
[also build test ERROR on v4.18-rc2 next-20180629]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Hari-Vyas/PCI-Data-corruption-happening-due-to-race-condition/20180629-203647
base:   https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git next
config: powerpc-defconfig (attached as .config)
compiler: powerpc64-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=powerpc 

Note: the linux-review/Hari-Vyas/PCI-Data-corruption-happening-due-to-race-condition/20180629-203647 HEAD 75ee48282af54fe77cb0ac092623577327440033 builds fine.
      It only hurts bisectibility.

All errors (new ones prefixed by >>):

   arch/powerpc/kernel/pci-common.c: In function 'pcibios_setup_bus_devices':
>> arch/powerpc/kernel/pci-common.c:1017:12: error: 'struct pci_dev' has no member named 'is_added'; did you mean 'is_managed'?
      if (dev->is_added)
               ^~~~~~~~
               is_managed

vim +1017 arch/powerpc/kernel/pci-common.c

7846de40 Guenter Roeck          2013-06-10  1005  
37f02195 Yuanquan Chen          2013-04-02  1006  void pcibios_setup_bus_devices(struct pci_bus *bus)
37f02195 Yuanquan Chen          2013-04-02  1007  {
37f02195 Yuanquan Chen          2013-04-02  1008  	struct pci_dev *dev;
37f02195 Yuanquan Chen          2013-04-02  1009  
37f02195 Yuanquan Chen          2013-04-02  1010  	pr_debug("PCI: Fixup bus devices %d (%s)\n",
37f02195 Yuanquan Chen          2013-04-02  1011  		 bus->number, bus->self ? pci_name(bus->self) : "PHB");
37f02195 Yuanquan Chen          2013-04-02  1012  
37f02195 Yuanquan Chen          2013-04-02  1013  	list_for_each_entry(dev, &bus->devices, bus_list) {
37f02195 Yuanquan Chen          2013-04-02  1014  		/* Cardbus can call us to add new devices to a bus, so ignore
37f02195 Yuanquan Chen          2013-04-02  1015  		 * those who are already fully discovered
37f02195 Yuanquan Chen          2013-04-02  1016  		 */
37f02195 Yuanquan Chen          2013-04-02 @1017  		if (dev->is_added)
37f02195 Yuanquan Chen          2013-04-02  1018  			continue;
37f02195 Yuanquan Chen          2013-04-02  1019  
37f02195 Yuanquan Chen          2013-04-02  1020  		pcibios_setup_device(dev);
37f02195 Yuanquan Chen          2013-04-02  1021  	}
7eef440a Benjamin Herrenschmidt 2008-10-27  1022  }
7eef440a Benjamin Herrenschmidt 2008-10-27  1023  

:::::: The code at line 1017 was first introduced by commit
:::::: 37f02195bee9c25ce44e25204f40b7961a6d7c9d powerpc/pci: fix PCI-e devices rescan issue on powerpc platform

:::::: TO: Yuanquan Chen <Yuanquan.Chen@freescale.com>
:::::: CC: Michael Ellerman <michael@ellerman.id.au>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 23810 bytes --]

Re: [PATCH v2 1/3] PCI: Data corruption happening due to race condition

[Lukas Wunner]

On Fri, Jun 29, 2018 at 03:57:39PM +0530, Hari Vyas wrote:
> Fix moves device addition is_added bit to separate private flag
> variable and use different atomic functions to set, clear and
> retrieve device addition state. As is_added shares different
> memory location so race condition is avoided.

As 0-day has already discovered, you need to squash all 3 patches
together to avoid breaking the build.


> +static inline int pci_dev_set_added(struct pci_dev *dev, void *unused)
> +{
> +	set_bit(PCI_DEV_ADDED, &dev->priv_flags);
> +	return 0;
> +}
> +
> +static inline int pci_dev_clear_added(struct pci_dev *dev, void *unused)
> +{
> +	clear_bit(PCI_DEV_ADDED, &dev->priv_flags);
> +	return 0;
> +}

You don't need the "unused" parameter here and you can return void.
pci_dev_set_disconnected() has the parameter because the function is
passed in to pci_walk_bus() in a few places, but you're not doing that
AFAICS.

What you *could* do however is collapse pci_dev_set_added() and
pci_dev_clear_added() into a single function, pass in a bool "added",
then use assign_bit() to set or clear it.  It would save 6 LoC.

Thanks,

Lukas

Re: [PATCH v2 1/3] PCI: Data corruption happening due to race condition

[Hari Vyas]

On Sun, Jul 1, 2018 at 7:36 PM, Lukas Wunner <lukas@wunner.de> wrote:
> On Fri, Jun 29, 2018 at 03:57:39PM +0530, Hari Vyas wrote:
>> Fix moves device addition is_added bit to separate private flag
>> variable and use different atomic functions to set, clear and
>> retrieve device addition state. As is_added shares different
>> memory location so race condition is avoided.
>
> As 0-day has already discovered, you need to squash all 3 patches
> together to avoid breaking the build.
>
>
Agreed. I will squash and raise a new patch
>> +static inline int pci_dev_set_added(struct pci_dev *dev, void *unused)
>> +{
>> +     set_bit(PCI_DEV_ADDED, &dev->priv_flags);
>> +     return 0;
>> +}
>> +
>> +static inline int pci_dev_clear_added(struct pci_dev *dev, void *unused)
>> +{
>> +     clear_bit(PCI_DEV_ADDED, &dev->priv_flags);
>> +     return 0;
>> +}
>
> You don't need the "unused" parameter here and you can return void.
> pci_dev_set_disconnected() has the parameter because the function is
> passed in to pci_walk_bus() in a few places, but you're not doing that
> AFAICS.
>
> What you *could* do however is collapse pci_dev_set_added() and
> pci_dev_clear_added() into a single function, pass in a bool "added",
> then use assign_bit() to set or clear it.  It would save 6 LoC.
>
Agreed.  Just for symmetry I did that one. Will incorporate change.
> Thanks,
>
> Lukas