BACKPORT: FROMLIST: PCI: sysfs: Guard pci_create_sysfs_dev_files with…

… atomic value

There is a race contition seen in rockchip platform which seems expose a long
existing bug in PCI sysfs code.

1. pci_bus_add_device() called pcibios_bus_add_device() or
pci_fixup_device() but have not called pci_create_sysfs_dev_files() yet.
Meanwhile pci_sysfs_init() is running and pci_create_sysfs_dev_files()
was called for newly registered device. In this case function
pci_create_sysfs_dev_files() is called two times, ones from
pci_bus_add_device() and once from pci_sysfs_init().

2. pci_sysfs_init() is called. It first sets sysfs_initialized to 1
which unblock calling pci_create_sysfs_dev_files(). Then another bus
registers new PCI device and calls pci_bus_add_device() which calls
pci_create_sysfs_dev_files() and registers sysfs files. Function
pci_sysfs_init() continues execution and calls function
pci_create_sysfs_dev_files() also for this newly registered device. So
pci_create_sysfs_dev_files() is again called two times.

The call trace looks like:

[    2.822232] [  T143] sysfs: cannot create duplicate filename '/devices/platform/fe170000.pcie/pci0002:20/0002:20:00.0/0002:21:00.0/config'
[    2.822240] [  T143] CPU: 1 PID: 143 Comm: rk-pcie Not tainted 5.10.66 rockchip-linux#56
[    2.822245] [  T143] Hardware name: Telpo RK3588 F206 Board (DT)
[    2.822251] [  T143] Call trace:
[    2.822262] [  T143]  dump_backtrace+0x0/0x1c8
[    2.822269] [  T143]  show_stack+0x1c/0x2c
[    2.822276] [  T143]  dump_stack_lvl+0xdc/0x12c
[    2.822282] [  T143]  dump_stack+0x1c/0x64
[    2.822289] [  T143]  sysfs_warn_dup+0x6c/0x8c
[    2.822296] [  T143]  sysfs_create_bin_file+0xe4/0x130
[    2.822303] [  T143]  pci_create_sysfs_dev_files+0x50/0x210
[    2.822310] [  T143]  pci_bus_add_device+0x30/0xac
[    2.822316] [  T143]  pci_bus_add_devices+0x44/0x88
[    2.822321] [  T143]  pci_bus_add_devices+0x70/0x88
[    2.822327] [  T143]  pci_host_probe+0x78/0xb0
[    2.822335] [  T143]  dw_pcie_host_init+0x308/0x3f8
[    2.822340] [  T143]  rk_pcie_really_probe+0x954/0xe04
[    2.822347] [  T143]  kthread+0x13c/0x344
[    2.822353] [  T143]  ret_from_fork+0x10/0x30

There are continuous reporting about this bug[1] can be found here[1].

The above link leads me to the fix[2]. Upstream kernel has contained the fix:
0ad52e381d85eb86906749e2b8073cdc2265844b ("Convert "config" to static attribute")
However there are still corner bugs around directory create. So Bijorn created
a Bugzilla item[3] for it. After a long time, Korneliusz Osmenda pushed a new
patch to fix it. Then we wait for another long period of time without any update.
IMO, [4] is better than other proposes. So just backport the better fix into vendor
tree.

[1] https: //lore.kernel.org/all/[email protected]/
[2] https: //patchwork.kernel.org/project/linux-pci/patch/[email protected]/
[3] Bug: https://bugzilla.kernel.org/show_bug.cgi?id=215515
[4] https: //patchwork.kernel.org/project/linux-pci/patch/[email protected]/
Signed-off-by: Korneliusz Osmenda <[email protected]>
Signed-off-by: Shawn Lin <[email protected]>
[Shawn: backport and reword to explain what happened]
Change-Id: Ib0a54bc2204afa7d9136e8d3156b00ec6aa4d8b3
(cherry-picked from https: //patchwork.kernel.org/project/linux-pci/patch/[email protected]/)

drivers/pci/pci-sysfs.c

@@ -1338,6 +1338,11 @@ int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev)
 	if (!sysfs_initialized)
 		return -EACCES;
 
+#ifdef CONFIG_NO_GKI
+	if (atomic_cmpxchg(&pdev->sysfs_init_cnt, 0, 1) == 1)
+		return 0; /* already added */
+#endif
+
 	if (pdev->cfg_size > PCI_CFG_SPACE_SIZE)
 		retval = sysfs_create_bin_file(&pdev->dev.kobj, &pcie_config_attr);
 	else
@@ -1417,6 +1422,11 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
 	if (!sysfs_initialized)
 		return;
 
+#ifdef CONFIG_NO_GKI
+	if (atomic_cmpxchg(&pdev->sysfs_init_cnt, 1, 0) == 0)
+		return;	/* already removed */
+#endif
+
 	pci_remove_capabilities_sysfs(pdev);
 
 	if (pdev->cfg_size > PCI_CFG_SPACE_SIZE)

include/linux/pci.h

@@ -453,6 +453,9 @@ struct pci_dev {
 	pci_dev_flags_t dev_flags;
 	atomic_t	enable_cnt;	/* pci_enable_device has been called */
 
+#ifdef CONFIG_NO_GKI
+	atomic_t	sysfs_init_cnt;		/* pci_create_sysfs_dev_files has been called */
+#endif
 	u32		saved_config_space[16]; /* Config space saved at suspend time */
 	struct hlist_head saved_cap_space;
 	struct bin_attribute *rom_attr;		/* Attribute descriptor for sysfs ROM entry */