Messages in this thread Patch in this message | | | From | "Ji-Ze Hong (Peter Hong)" <> | Subject | [PATCH 1/1] driver core: Fix unbalance probe_count in really_probe() | Date | Wed, 3 Jun 2020 14:45:09 +0800 |
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In previous patch, using return -EBUSY in really_probe() instead WARN_ON() only. The following is the partial code.
... atomic_inc(&probe_count); pr_debug("bus: '%s': %s: probing driver %s with device %s\n", drv->bus->name, __func__, drv->name, dev_name(dev)); if (!list_empty(&dev->devres_head)) { dev_crit(dev, "Resources present before probing\n"); return -EBUSY; } ...
When the devres_head is not empty, this code will return -EBUSY to prevent resource conflict, but it forgot to balance probe_count. We can move the increasement code below the resource checking.
... pr_debug("bus: '%s': %s: probing driver %s with device %s\n", drv->bus->name, __func__, drv->name, dev_name(dev)); if (!list_empty(&dev->devres_head)) { dev_crit(dev, "Resources present before probing\n"); return -EBUSY; } atomic_inc(&probe_count); ...
The original code will cause lots motherboard freeze in reboot/shutdown with systemd message "Reached target Reboot" or "Reached target Shutdown" with serial8250 platform driver. e.g. AOPEN DE6200. The conflict boot dmesg below:
Serial: 8250/16550 driver, 32 ports, IRQ sharing enabled 00:03: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 921600) is a 16550A 00:04: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 921600) is a 16550A 00:05: ttyS2 at I/O 0x3e8 (irq = 5, base_baud = 921600) is a 16550A serial8250: ttyS3 at I/O 0x2e8 (irq = 3, base_baud = 921600) is a 16550A
Reboot/Shutdown will freeze in wait_for_device_probe(), message as following: INFQ: task systemd-shutdown: 1 blocked for more than 120 seconds. Not tainted 5.7.0-rc7-tty-next+ #241 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Call Trace: __schedule+0x3d2/0x700 ? printk+0x52/0x6e schedule+0x4f/0xc0 wait_for_device_probe+0xbb/0xl40 ? wait_woken+0x80/0x80 device_shutdown+0xl5/0xle0 kernel_power_off+0x35/0x70 __do_sys_reboot+0xla0/0x220 ? do_sigtimedwait+0xld0/0x210 ? do.writev+0x6a/0xll0 ? do.writev+0x6a/0xll0 ? sigprocmask+0x6f/Oxa0 __64_sys_reboot+0xle/0x20 do_syscall_64+0x57/0xlb0
Fixes: 7c35e699c88b ("driver core: Print device when resources present in really_probe()") Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com> --- drivers/base/dd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 9a1d940342ac..5173b0766a26 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -487,7 +487,6 @@ static int really_probe(struct device *dev, struct device_driver *drv) if (ret) return ret; - atomic_inc(&probe_count); pr_debug("bus: '%s': %s: probing driver %s with device %s\n", drv->bus->name, __func__, drv->name, dev_name(dev)); if (!list_empty(&dev->devres_head)) { @@ -495,6 +494,8 @@ static int really_probe(struct device *dev, struct device_driver *drv) return -EBUSY; } + atomic_inc(&probe_count); + re_probe: dev->driver = drv; -- 2.17.1
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