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我正在编写一个内核驱动程序，通过i2c接口，我在多个地方从总线接口芯片读取数据。有些是通过ioctl从用户空间完成的，而另一些是在中断时发生的。从ioctl完成的读取工作正常，但从中断完成的读取会导致核心转储（请参阅下文）。内核函数在中断上失败，但不在ioctl上
下面是相关的代码部分：
static struct i2c_client *pcf8575_client; //global i2c client handle
static void
pcf8575_init_client(struct i2c_client *client) {
.
.
.
pcf8575_client = client;
.
.
.
}
static int
pcf8575_ioctl(struct inode *inode,struct file *file,unsigned int request,unsigned long argument)
{
.
.
.
pcf8575_read_char(pcf8575_client, &key); //works fine here, gets back appropriate value
.
.
.
}
static irqreturn_t i2c_keys_isr (int irq, void *data)
{
int result;
static char last_key, key;
static struct i2c_client *pcf8575_client;
pcf8575_client = (struct i2c_client*) data;
.
.
.
result = pcf8575_read_char (pcf8575_client, &key); //this is where it fails from the irq routine
}
//Here is the functions definition
static inline int
pcf8575_read(struct i2c_client *client, u8 reg, u8 *value) {
s32 data;
data = i2c_smbus_read_byte_data(client, reg); //fails on this call only when called from the interrupt
if (data < 0)
return -EIO;
*value = data;
return 0;
}
我们已经证实，pcf8575_client是一种有效的非空指针，我们能够打印出指针的值，并确认其符合全球以及从中断例程中指针指向的结构中取消引用各个值。
这是我们收到的核心转储：
BUG: scheduling while atomic: swapper/0/0x00010000
Modules linked in: i2c_keys<7>s3c2410-i2c s3c2410-i2c: READ: Send Stop
Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 0 [#1]
Modules linked in: i2c_keys i2cts(P) gpio
CPU: 0 Tainted: P (2.6.28.10 #143)
PC is at 0x0
LR is at activate_task+0x48/0x60
pc : [<00000000>] lr : [<c0080560>] psr: 40000093
sp : c0347b80 ip : c0347b98 fp : c0347b94
r10: 00000000 r9 : 00000003 r8 : c035e7b8
r7 : 00000000 r6 : 20000093 r5 : c0364f60 r4 : c0348fe4
r3 : c0299098 r2 : 00000001 r1 : c0348fe4 r0 : c0364f60
Flags: nZcv IRQs off FIQs on Mode SVC_32 ISA ARM Segment kernel
Control: c000717f Table: 3fbb0000 DAC: 00000017
Process swapper (pid: 0, stack limit = 0xc0346260)
Stack: (0xc0347b80 to 0xc0348000)
7b80: c0348fe4 c035e7ac c0347bb4 c0347b98 c00819e4 c0080528 c0347e24 c035e7ac
7ba0: 00000000 00000001 c0347bc4 c0347bb8 c0081a5c c0081994 c0347bd8 c0347bc8
7bc0: c00994fc c0081a58 c0347e24 c0347c04 c0347bdc c0080a74 c00994f8 60000093
7be0: c035e7b8 00000000 0000002b 00000009 00000000 c0346000 c0347c1c c0347c08
7c00: c0080ae4 c0080a4c 00000000 00000091 c0347c40 c0347c20 c020fde4 c0080ac8
7c20: cfaaffc0 00000000 00000000 0000002b 00000009 c0347c60 c0347c44 c00a888c
7c40: c020fc70 c03518e0 0000002b cfaaffc0 c037832c c0347c80 c0347c64 c00a9d40
7c60: c00a8858 0000002b c0347f4c 08000000 c0347d70 c0347c98 c0347c84 c0072064
7c80: c00a9c40 ffffffff f4000000 c0347d58 c0347c9c c0072a44 c0072010 c034f50c
7ca0: 80000013 c034f4cc c034f4cc c0375864 00000000 c037586d c0347d70 00000009
7cc0: 00000000 c0346000 c0347d58 c0347cb8 c0347ce4 c0085b48 c0086158 60000013
7ce0: ffffffff c034f52c c034f52c c0347d7c c0347cdc 00000004 80000013 c0086158
7d00: 60000013 ffffffff c034e430 c0347d28 c0347d1c c007d440 00000003 60000013
7d20: c0347d58 c0347d30 c0085b48 c009ce50 bf00b420 c0350dd4 c0347d7c 000003e8
7d40: c0364f60 00000000 c0346000 c0347d68 c0347d5c c02962fc c0085eb4 c0347d9c
7d60: c0347d7c c00a43e0 c02962f4 c030252e bf00b42c c0347d7c 00000000 c0085e00
7d80: c0347db0 c0347f4c c0348fe4 c034913c c0347db0 c0347da0 c0082e7c c00a43a4
7da0: ffff4a0b c0347ddc c0347db4 c0296740 c0082e58 ffff4a0b c0347de0 c0350238
7dc0: 000003e8 c0346000 c0347e30 c0347e24 c0347e14 c0347de0 c0296ba0 c0296704
7de0: c0376678 c0376678 ffff4a0b c008ecd4 c0348fe4 c0375e20 000003e8 c035e7b8
7e00: 00000000 00000000 c0347e60 c0347e18 c020fb7c c0296b18 00000001 c0347eac
7e20: c035e7f4 00000000 c0348fe4 c00994e8 c035e7b8 c035e7b8 00000052 c02fbb1d
7e40: 00000002 c035e7f4 c0347eb8 c035e834 00000001 c0347ea8 c0347e64 c020c290
7e60: c020fa20 00000052 00000021 00000002 c02fbb1d c035e8c0 00000001 c0347eac
7e80: c035e7f4 00000021 c0347eda 00000002 30020fdc 41129200 30020f40 c0347ed4
7ea0: c0347eac c020d018 c020c198 00010021 c0290002 c0347eda cfba5e00 00000000
7ec0: 00000000 00000010 c0347ef0 c0347ed8 bf00a2b4 c020cfd0 ffff7f10 cfbbe300
7ee0: 00000000 c0347f10 c0347ef4 c00a888c bf00a25c c035128c 00000010 cfbbe300
7f00: c037832c c0347f30 c0347f14 c00a9d40 c00a8858 00000010 00000000 00000001
7f20: c03644e8 c0347f48 c0347f34 c0072064 c00a9c40 ffffffff f4000000 c0347fa0
7f40: c0347f4c c0072a44 c0072010 f4100000 00000032 f4100000 60000013 c00738f8
7f60: c0346000 c00738f8 c03644e8 30020fdc 41129200 30020f40 c0347fa0 c0347fa4
7f80: c0347f94 c0073f08 c0073998 60000013 ffffffff c0347fc0 c0347fa4 c0073f08
7fa0: c0073908 c03786d8 c0364088 c0022f00 c0349c34 c0347fd0 c0347fc4 c0295258
7fc0: c0073ed8 c0347ff4 c0347fd4 c000896c c0295214 c0008458 c0022f00 c0007175
7fe0: c036454c c0023304 00000000 c0347ff8 30008034 c0008704 00000000 00000000
Backtrace:
[<c0080518>] (activate_task+0x0/0x60) from [<c00819e4>] (try_to_wake_up+0x60/0xc4)
r5:c035e7ac r4:c0348fe4
[<c0081984>] (try_to_wake_up+0x0/0xc4) from [<c0081a5c>] (default_wake_function+0x14/0x18)
r7:00000001 r6:00000000 r5:c035e7ac r4:c0347e24
[<c0081a48>] (default_wake_function+0x0/0x18) from [<c00994fc>] (autoremove_wake_function+0x14/0x3c)
[<c00994e8>] (autoremove_wake_function+0x0/0x3c) from [<c0080a74>] (__wake_up_common+0x38/0x7c)
r4:c0347e24
[<c0080a3c>] (__wake_up_common+0x0/0x7c) from [<c0080ae4>] (__wake_up+0x2c/0x44)
[<c0080ab8>] (__wake_up+0x0/0x44) from [<c020fde4>] (s3c24xx_i2c_irq+0x184/0x5c4)
r4:00000091
[<c020fc60>] (s3c24xx_i2c_irq+0x0/0x5c4) from [<c00a888c>] (handle_IRQ_event+0x44/0x80)
r8:00000009 r7:0000002b r6:00000000 r5:00000000 r4:cfaaffc0
[<c00a8848>] (handle_IRQ_event+0x0/0x80) from [<c00a9d40>] (handle_edge_irq+0x110/0x14c)
r7:c037832c r6:cfaaffc0 r5:0000002b r4:c03518e0
[<c00a9c30>] (handle_edge_irq+0x0/0x14c) from [<c0072064>] (__exception_text_start+0x64/0x84)
r7:c0347d70 r6:08000000 r5:c0347f4c r4:0000002b
[<c0072000>] (__exception_text_start+0x0/0x84) from [<c0072a44>] (__irq_svc+0x24/0xa0)
Exception stack(0xc0347c9c to 0xc0347ce4)
7c80: c034f50c
7ca0: 80000013 c034f4cc c034f4cc c0375864 00000000 c037586d c0347d70 00000009
7cc0: 00000000 c0346000 c0347d58 c0347cb8 c0347ce4 c0085b48 c0086158 60000013
7ce0: ffffffff
r5:f4000000 r4:ffffffff
[<c0085ea4>] (vprintk+0x0/0x2fc) from [<c02962fc>] (printk+0x1c/0x24)
[<c02962e0>] (printk+0x0/0x24) from [<c00a43e0>] (print_modules+0x4c/0x9c)
r3:00000000 r2:c0347d7c r1:bf00b42c r0:c030252e
[<c00a4394>] (print_modules+0x0/0x9c) from [<c0082e7c>] (__schedule_bug+0x34/0x5c)
r6:c034913c r5:c0348fe4 r4:c0347f4c
[<c0082e48>] (__schedule_bug+0x0/0x5c) from [<c0296740>] (schedule+0x4c/0x2b8)
r4:ffff4a0b
[<c02966f4>] (schedule+0x0/0x2b8) from [<c0296ba0>] (schedule_timeout+0x98/0xc4)
[<c0296b08>] (schedule_timeout+0x0/0xc4) from [<c020fb7c>] (s3c24xx_i2c_xfer+0x16c/0x250)
r7:00000000 r6:00000000 r5:c035e7b8 r4:000003e8
[<c020fa10>] (s3c24xx_i2c_xfer+0x0/0x250) from [<c020c290>] (i2c_transfer+0x108/0x168)
[<c020c188>] (i2c_transfer+0x0/0x168) from [<c020d018>] (i2c_master_recv+0x58/0x80)
[<c020cfc0>] (i2c_master_recv+0x0/0x80) from [<bf00a2b4>] (i2c_keys_isr+0x68/0x1b4 [i2c_keys])
r7:00000010 r6:00000000 r5:00000000 r4:cfba5e00
[<bf00a24c>] (i2c_keys_isr+0x0/0x1b4 [i2c_keys]) from [<c00a888c>] (handle_IRQ_event+0x44/0x80)
r5:00000000 r4:cfbbe300
[<c00a8848>] (handle_IRQ_event+0x0/0x80) from [<c00a9d40>] (handle_edge_irq+0x110/0x14c)
r7:c037832c r6:cfbbe300 r5:00000010 r4:c035128c
[<c00a9c30>] (handle_edge_irq+0x0/0x14c) from [<c0072064>] (__exception_text_start+0x64/0x84)
r7:c03644e8 r6:00000001 r5:00000000 r4:00000010
[<c0072000>] (__exception_text_start+0x0/0x84) from [<c0072a44>] (__irq_svc+0x24/0xa0)
Exception stack(0xc0347f4c to 0xc0347f94)
7f40: f4100000 00000032 f4100000 60000013 c00738f8
7f60: c0346000 c00738f8 c03644e8 30020fdc 41129200 30020f40 c0347fa0 c0347fa4
7f80: c0347f94 c0073f08 c0073998 60000013 ffffffff
r5:f4000000 r4:ffffffff
[<c00738f8>] (default_idle+0x0/0xb0) from [<c0073f08>] (cpu_idle+0x40/0x5c)
[<c0073ec8>] (cpu_idle+0x0/0x5c) from [<c0295258>] (rest_init+0x54/0x68)
r7:c0349c34 r6:c0022f00 r5:c0364088 r4:c03786d8
[<c0295204>] (rest_init+0x0/0x68) from [<c000896c>] (start_kernel+0x278/0x2e0)
[<c00086f4>] (start_kernel+0x0/0x2e0) from [<30008034>] (0x30008034)
r6:c0023304 r5:c036454c r4:c0007175
Code: bad PC value.
Kernel panic - not syncing: Fatal exception in interrupt
对于不是“核心转储”的记录，它是来自内核的“bug”或“oops”报告。 – mpe 2011-04-20 01:20:16