When the test 'CONFIG_DEBUG_TEST_DRIVER_REMOVE=y' is enabled,
arch_initcall(pl011_init) came before subsys_initcall(default_bdi_init).
devtmpfs gets killed because we try to remove a file and decrement the
wb reference count before the noop_backing_device_info gets initialized.
[ 0.332075] Serial: AMBA PL011 UART driver
[ 0.485276] 9000000.pl011: ttyAMA0 at MMIO 0x9000000 (irq = 39, base_baud = 0) is a PL011 rev1
[ 0.502382] console [ttyAMA0] enabled
[ 0.515710] Unable to handle kernel paging request at virtual address 0000800074c12000
[ 0.516053] Mem abort info:
[ 0.516222] ESR = 0x96000004
[ 0.516417] Exception class = DABT (current EL), IL = 32 bits
[ 0.516641] SET = 0, FnV = 0
[ 0.516826] EA = 0, S1PTW = 0
[ 0.516984] Data abort info:
[ 0.517149] ISV = 0, ISS = 0x00000004
[ 0.517339] CM = 0, WnR = 0
[ 0.517553] [0000800074c12000] user address but active_mm is swapper
[ 0.517928] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[ 0.518305] Modules linked in:
[ 0.518839] CPU: 0 PID: 13 Comm: kdevtmpfs Not tainted 4.19.0-rc5-next-20180928-00002-g2ba39ab0cd01-dirty #82
[ 0.519307] Hardware name: linux,dummy-virt (DT)
[ 0.519681] pstate: 80000005 (Nzcv daif -PAN -UAO)
[ 0.519959] pc : __destroy_inode+0x94/0x2a8
[ 0.520212] lr : __destroy_inode+0x78/0x2a8
[ 0.520401] sp : ffff0000098c3b20
[ 0.520590] x29: ffff0000098c3b20 x28: 00000000087a3714
[ 0.520904] x27: 0000000000002000 x26: 0000000000002000
[ 0.521179] x25: ffff000009583000 x24: 0000000000000000
[ 0.521467] x23: ffff80007bb52000 x22: ffff80007bbaa7c0
[ 0.521737] x21: ffff0000093f9338 x20: 0000000000000000
[ 0.522033] x19: ffff80007bbb05d8 x18: 0000000000000400
[ 0.522376] x17: 0000000000000000 x16: 0000000000000000
[ 0.522727] x15: 0000000000000400 x14: 0000000000000400
[ 0.523068] x13: 0000000000000001 x12: 0000000000000001
[ 0.523421] x11: 0000000000000000 x10: 0000000000000970
[ 0.523749] x9 : ffff0000098c3a60 x8 : ffff80007bbab190
[ 0.524017] x7 : ffff80007bbaa880 x6 : 0000000000000c88
[ 0.524305] x5 : ffff0000093d96c8 x4 : 61c8864680b583eb
[ 0.524567] x3 : ffff0000093d6180 x2 : ffffffffffffffff
[ 0.524872] x1 : 0000800074c12000 x0 : 0000800074c12000
[ 0.525207] Process kdevtmpfs (pid: 13, stack limit = 0x(____ptrval____))
[ 0.525529] Call trace:
[ 0.525806] __destroy_inode+0x94/0x2a8
[ 0.526108] destroy_inode+0x34/0x88
[ 0.526370] evict+0x144/0x1c8
[ 0.526636] iput+0x184/0x230
[ 0.526871] dentry_unlink_inode+0x118/0x130
[ 0.527152] d_delete+0xd8/0xe0
[ 0.527420] vfs_unlink+0x240/0x270
[ 0.527665] handle_remove+0x1d8/0x330
[ 0.527875] devtmpfsd+0x138/0x1c8
[ 0.528085] kthread+0x14c/0x158
[ 0.528291] ret_from_fork+0x10/0x18
[ 0.528720] Code: 92800002 aa1403e0 d538d081 8b010000 (c85f7c04)
[ 0.529367] ---[ end trace 5a3dee47727f877c ]---
Rework to set suppress_bind_attrs flag to avoid removing the device when
CONFIG_DEBUG_TEST_DRIVER_REMOVE=y. This applies for pic32_uart and
xilinx_uartps as well.
Co-developed-by: Arnd Bergmann <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Anders Roxell <[email protected]>
---
drivers/tty/serial/amba-pl011.c | 2 ++
drivers/tty/serial/pic32_uart.c | 1 +
drivers/tty/serial/xilinx_uartps.c | 1 +
3 files changed, 4 insertions(+)
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index ebd33c0232e6..89ade213a1a9 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2780,6 +2780,7 @@ static struct platform_driver arm_sbsa_uart_platform_driver = {
.name = "sbsa-uart",
.of_match_table = of_match_ptr(sbsa_uart_of_match),
.acpi_match_table = ACPI_PTR(sbsa_uart_acpi_match),
+ .suppress_bind_attrs = IS_BUILTIN(CONFIG_SERIAL_AMBA_PL011),
},
};
@@ -2808,6 +2809,7 @@ static struct amba_driver pl011_driver = {
.drv = {
.name = "uart-pl011",
.pm = &pl011_dev_pm_ops,
+ .suppress_bind_attrs = IS_BUILTIN(CONFIG_SERIAL_AMBA_PL011),
},
.id_table = pl011_ids,
.probe = pl011_probe,
diff --git a/drivers/tty/serial/pic32_uart.c b/drivers/tty/serial/pic32_uart.c
index fd80d999308d..0bdf1687983f 100644
--- a/drivers/tty/serial/pic32_uart.c
+++ b/drivers/tty/serial/pic32_uart.c
@@ -919,6 +919,7 @@ static struct platform_driver pic32_uart_platform_driver = {
.driver = {
.name = PIC32_DEV_NAME,
.of_match_table = of_match_ptr(pic32_serial_dt_ids),
+ .suppress_bind_attrs = IS_BUILTIN(CONFIG_SERIAL_PIC32),
},
};
diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 57c66d2c3471..379242b96790 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1719,6 +1719,7 @@ static struct platform_driver cdns_uart_platform_driver = {
.name = CDNS_UART_NAME,
.of_match_table = cdns_uart_of_match,
.pm = &cdns_uart_dev_pm_ops,
+ .suppress_bind_attrs = IS_BUILTIN(CONFIG_SERIAL_XILINX_PS_UART),
},
};
--
2.19.1
This happened while running in qemu-system-aarch64, the AMBA PL011 UART
driver when enabling CONFIG_DEBUG_TEST_DRIVER_REMOVE.
arch_initcall(pl011_init) came before subsys_initcall(default_bdi_init),
devtmpfs' handle_remove() crashes because the reference count is a NULL
pointer only because wb->bdi hasn't been initialized yet.
Rework so that wb_put have an extra check if wb->bdi before decrement
wb->refcnt and also add a WARN_ON_ONCE to get a warning if it happens again
in other drivers.
Fixes: 52ebea749aae ("writeback: make backing_dev_info host cgroup-specific bdi_writebacks")
Co-developed-by: Arnd Bergmann <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Anders Roxell <[email protected]>
---
include/linux/backing-dev-defs.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 9a6bc0951cfa..c31157135598 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -258,6 +258,14 @@ static inline void wb_get(struct bdi_writeback *wb)
*/
static inline void wb_put(struct bdi_writeback *wb)
{
+ if (WARN_ON_ONCE(!wb->bdi)) {
+ /*
+ * A driver bug might cause a file to be removed before bdi was
+ * initialized.
+ */
+ return;
+ }
+
if (wb != &wb->bdi->wb)
percpu_ref_put(&wb->refcnt);
}
--
2.19.1