Description of problem: when execute a simple delete_module program like (the ext3 module is in-use): main() { delete_module("ext3"); } The program often hang and after several minutes, kernel oops message given: INFO: task a.out:4172 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. a.out D ffffffff80151248 0 4172 1 4002 (NOTLB) ffff810063b09ef8 0000000000000086 000000048008e16d ffffffff804a16f0 ffffffff804a16f8 0000000000000007 ffff81007e8770c0 ffff81007fe487a0 0000029cb2d0be13 00000000000049e9 ffff81007e8772a8 000000007e8770c0 Call Trace: [<ffffffff800a77c1>] sys_delete_module+0x15c/0x1c5 [<ffffffff8005e28d>] tracesys+0xd5/0xe0 INFO: task a.out:4172 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. a.out D ffffffff80151248 0 4172 1 4002 (NOTLB) ffff810063b09ef8 0000000000000086 000000048008e16d ffffffff804a16f0 ffffffff804a16f8 0000000000000007 ffff81007e8770c0 ffff81007fe487a0 0000029cb2d0be13 00000000000049e9 ffff81007e8772a8 000000007e8770c0 Call Trace: [<ffffffff800a77c1>] sys_delete_module+0x15c/0x1c5 [<ffffffff8005e28d>] tracesys+0xd5/0xe0 Version-Release number of selected component (if applicable): 2.6.18-194.el5 How reproducible: >80% Steps to Reproduce: 1. see above 2. 3. Actual results: kernel oops Expected results: no oops and program can finish execution Additional info: strace ./a.out: execve("./a.out", ["./a.out"], [/* 23 vars */]) = 0 brk(0) = 0x10bd4000 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ac6b41bb000 uname({sys="Linux", node="dell-p690-01.rhts.eng.bos.redhat.com", ...}) = 0 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) open("/etc/ld.so.cache", O_RDONLY) = 3 fstat(3, {st_mode=S_IFREG|0644, st_size=81122, ...}) = 0 mmap(NULL, 81122, PROT_READ, MAP_PRIVATE, 3, 0) = 0x2ac6b41bc000 close(3) = 0 open("/lib64/libc.so.6", O_RDONLY) = 3 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\220\332\341\3022\0\0\0"..., 832) = 832 fstat(3, {st_mode=S_IFREG|0755, st_size=1717800, ...}) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ac6b41d0000 mmap(0x32c2e00000, 3498328, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x32c2e00000 mprotect(0x32c2f4e000, 2093056, PROT_NONE) = 0 mmap(0x32c314d000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x14d000) = 0x32c314d000 mmap(0x32c3152000, 16728, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x32c3152000 close(3) = 0 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ac6b41d1000 arch_prctl(ARCH_SET_FS, 0x2ac6b41d1210) = 0 mprotect(0x32c314d000, 16384, PROT_READ) = 0 mprotect(0x32c2c1b000, 4096, PROT_READ) = 0 munmap(0x2ac6b41bc000, 81122) = 0 delete_module("ext3", O_RDONLY|O_ASYNC|O_LARGEFILE|O_NOFOLLOW|O_NOATIME|0xf5700028
This is not a crash, or an oops, it is a hung task.
If you compile your test looking for warnings, you will get: # gcc -Wall -o test test.c stupid.c:2: warning: return type defaults to ‘int’ stupid.c: In function ‘main’: stupid.c:3: warning: implicit declaration of function ‘delete_module’ stupid.c:4: warning: control reaches end of non-void function Note the implicit declaration of delete_module. I think that you are missing a flags argument, which could cause the call to return -EBUSY rather than hang on a busy module. I don't think this is a kernel bug. -Eric
With the right combination of (random, unspecified) flags, this is the same as doing "rmmod -w": -w --wait Normally, rmmod will refuse to unload modules which are in use. With this option, rmmod will isolate the module, and wait until the module is no longer used. Noone new will be able to use the module, but it’s up to you to make sure the current users even- tually finish with it. See lsmod(8)) for information on usage counts.