[linux-pm] [patch] revert: "ACPI: drivers/acpi: elide a non-zero test on a result that is never 0"
Ingo Molnar
mingo at elte.hu
Fri Mar 28 06:59:37 PDT 2008
* Len Brown <lenb at kernel.org> wrote:
> I've not used "-b" until now. I added it because Julia's patch was
> simple, but since it changed indenting of a couple of blocks its
> diffstat was otherwise large.
> Julia Lawall (1):
> ACPI: drivers/acpi: elide a non-zero test on a result that is never 0
overnight randconfig qa on x86.git/latest triggered a bootup crash after
just 7 iterations, which i bisected down to the commit above. Find the
revert below.
Observation: the patch was just 3 days old when it went upstream and
given that it touches 50 lines of code executed on most PC hardware
during bootup so i dont think it was in the trivial category.
Even if the fix is right (which is does look to be at first sight),
there's clearly some side-effect here and the whitespace changes mixed
into the functional changes make it hard to validate this change.
now that i had a second look, one side-effect seems to be:
+ acpi_driver_data(device) = cdev;
this used to be executed before even with a NULL cdev and isnt executed
now. (In any case, the revert below is the right thing to do i believe,
the patch should have its clock reset and should restart its testing
cycle at the tail of the development queue.)
Ingo
---------------------->
Subject: revert "ACPI: drivers/acpi: elide a non-zero test on a result that is never 0"
From: Ingo Molnar <mingo at elte.hu>
Date: Fri Mar 28 14:28:03 CET 2008
revert:
ACPI: drivers/acpi: elide a non-zero test on a result that is never 0
as randconfig testing found that it causes a crash during bootup:
initcall 0x78878534 ran for 13 msecs: acpi_button_init+0x0/0x51()
Calling initcall 0x78878585: acpi_fan_init+0x0/0x2c()
BUG: unable to handle kernel NULL pointer dereference at 00000000
IP: [<782b8ad0>] acpi_fan_add+0x7d/0xfd
*pde = 00000000
Oops: 0000 [#1]
Modules linked in:
Pid: 1, comm: swapper Not tainted (2.6.25-rc7-sched-devel.git-x86-latest.git #14)
EIP: 0060:[<782b8ad0>] EFLAGS: 00010246 CPU: 0
EIP is at acpi_fan_add+0x7d/0xfd
EAX: b787c718 EBX: b787c400 ECX: b782ceb4 EDX: 00000007
ESI: 00000000 EDI: b787c6f4 EBP: b782cee0 ESP: b782cecc
DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068
Process swapper (pid: 1, ti=b782c000 task=b7846000 task.ti=b782c000)
Stack: b787c459 00000000 b787c400 78790888 b787c60c b782cef8 782b6fb8 ffffffda
b787c60c 00000000 78790958 b782cf0c 783005d7 b787c60c 78790958 78790584
b782cf1c 783007f6 b782cf28 00000000 b782cf40 782ffc4a 78790958 b794d558
Call Trace:
[<782b6fb8>] ? acpi_device_probe+0x3e/0xdb
[<783005d7>] ? driver_probe_device+0x82/0xfc
[<783007f6>] ? __driver_attach+0x3a/0x70
[<782ffc4a>] ? bus_for_each_dev+0x3e/0x60
[<7830048c>] ? driver_attach+0x14/0x16
[<783007bc>] ? __driver_attach+0x0/0x70
[<7830006a>] ? bus_add_driver+0x9d/0x1b0
[<783008c3>] ? driver_register+0x47/0xa3
[<7813db00>] ? timespec_to_ktime+0x9/0xc
[<782b7331>] ? acpi_bus_register_driver+0x3a/0x3c
[<78878592>] ? acpi_fan_init+0xd/0x2c
[<78863656>] ? kernel_init+0xac/0x1f9
[<788635aa>] ? kernel_init+0x0/0x1f9
[<78114563>] ? kernel_thread_helper+0x7/0x10
=======================
Code: 6e 78 e8 57 44 e7 ff 58 e9 93 00 00 00 8b 55 f0 8d bb f4 02 00 00 80 4b 2d 10 8b 03 e8 87 cb ff ff 8d 83 18 03 00 00 80 63 2d ef <ff> 35 00 00 00 00 50 68 e8 9c 6e 78 e8 22 44 e7 ff b9 b6 9c 6e
EIP: [<782b8ad0>] acpi_fan_add+0x7d/0xfd SS:ESP 0068:b782cecc
---[ end trace 778e504de7e3b1e3 ]---
Kernel panic - not syncing: Attempted to kill init!
Signed-off-by: Ingo Molnar <mingo at elte.hu>
---
drivers/acpi/fan.c | 34 ++++++++++++++++++----------------
drivers/acpi/processor_core.c | 30 ++++++++++++++++--------------
drivers/acpi/video.c | 28 +++++++++++++++-------------
3 files changed, 49 insertions(+), 43 deletions(-)
Index: linux-x86.q/drivers/acpi/fan.c
===================================================================
--- linux-x86.q.orig/drivers/acpi/fan.c
+++ linux-x86.q/drivers/acpi/fan.c
@@ -260,22 +260,24 @@ static int acpi_fan_add(struct acpi_devi
result = PTR_ERR(cdev);
goto end;
}
- printk(KERN_INFO PREFIX
- "%s is registered as cooling_device%d\n",
- device->dev.bus_id, cdev->id);
-
- acpi_driver_data(device) = cdev;
- result = sysfs_create_link(&device->dev.kobj,
- &cdev->device.kobj,
- "thermal_cooling");
- if (result)
- return result;
-
- result = sysfs_create_link(&cdev->device.kobj,
- &device->dev.kobj,
- "device");
- if (result)
- return result;
+ if (cdev) {
+ printk(KERN_INFO PREFIX
+ "%s is registered as cooling_device%d\n",
+ device->dev.bus_id, cdev->id);
+
+ acpi_driver_data(device) = cdev;
+ result = sysfs_create_link(&device->dev.kobj,
+ &cdev->device.kobj,
+ "thermal_cooling");
+ if (result)
+ return result;
+
+ result = sysfs_create_link(&cdev->device.kobj,
+ &device->dev.kobj,
+ "device");
+ if (result)
+ return result;
+ }
result = acpi_fan_add_fs(device);
if (result)
Index: linux-x86.q/drivers/acpi/processor_core.c
===================================================================
--- linux-x86.q.orig/drivers/acpi/processor_core.c
+++ linux-x86.q/drivers/acpi/processor_core.c
@@ -674,20 +674,22 @@ static int __cpuinit acpi_processor_star
result = PTR_ERR(pr->cdev);
goto end;
}
- printk(KERN_INFO PREFIX
- "%s is registered as cooling_device%d\n",
- device->dev.bus_id, pr->cdev->id);
-
- result = sysfs_create_link(&device->dev.kobj,
- &pr->cdev->device.kobj,
- "thermal_cooling");
- if (result)
- return result;
- result = sysfs_create_link(&pr->cdev->device.kobj,
- &device->dev.kobj,
- "device");
- if (result)
- return result;
+ if (pr->cdev) {
+ printk(KERN_INFO PREFIX
+ "%s is registered as cooling_device%d\n",
+ device->dev.bus_id, pr->cdev->id);
+
+ result = sysfs_create_link(&device->dev.kobj,
+ &pr->cdev->device.kobj,
+ "thermal_cooling");
+ if (result)
+ return result;
+ result = sysfs_create_link(&pr->cdev->device.kobj,
+ &device->dev.kobj,
+ "device");
+ if (result)
+ return result;
+ }
if (pr->flags.throttling) {
printk(KERN_INFO PREFIX "%s [%s] (supports",
Index: linux-x86.q/drivers/acpi/video.c
===================================================================
--- linux-x86.q.orig/drivers/acpi/video.c
+++ linux-x86.q/drivers/acpi/video.c
@@ -734,19 +734,21 @@ static void acpi_video_device_find_cap(s
if (IS_ERR(device->cdev))
return;
- printk(KERN_INFO PREFIX
- "%s is registered as cooling_device%d\n",
- device->dev->dev.bus_id, device->cdev->id);
- result = sysfs_create_link(&device->dev->dev.kobj,
- &device->cdev->device.kobj,
- "thermal_cooling");
- if (result)
- printk(KERN_ERR PREFIX "Create sysfs link\n");
- result = sysfs_create_link(&device->cdev->device.kobj,
- &device->dev->dev.kobj,
- "device");
- if (result)
- printk(KERN_ERR PREFIX "Create sysfs link\n");
+ if (device->cdev) {
+ printk(KERN_INFO PREFIX
+ "%s is registered as cooling_device%d\n",
+ device->dev->dev.bus_id, device->cdev->id);
+ result = sysfs_create_link(&device->dev->dev.kobj,
+ &device->cdev->device.kobj,
+ "thermal_cooling");
+ if (result)
+ printk(KERN_ERR PREFIX "Create sysfs link\n");
+ result = sysfs_create_link(&device->cdev->device.kobj,
+ &device->dev->dev.kobj,
+ "device");
+ if (result)
+ printk(KERN_ERR PREFIX "Create sysfs link\n");
+ }
}
if (device->cap._DCS && device->cap._DSS){
static int count = 0;
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