event loop and should sleep only when waiting for events (eg. via kevent(2)).
When a program is going to sleep in the kernel, the script will show its name,
PID, kernel stack trace and userland stack trace. Sleeping in kevent(2) is
ignored as it is expected to be valid.
Sample output:
# ./blocking lynxd
lynxd(15042) is blocking...
kernel`_cv_wait_sig+0x124
kernel`seltdwait+0xae
kernel`sys_poll+0x3a3
kernel`amd64_syscall+0x343
kernel`0xffffffff806c79ab
lynxd`poll+0xa
lynxd`pqSocketCheck+0xa2
lynxd`pqWaitTimed+0x29
lynxd`connectDBComplete+0xd7
lynxd`PQsetdbLogin+0x2ec
lynxd`db_connect+0x3c
lynxd`main+0x198
lynxd`_start+0x16f
0x2
lynxd(1925) is blocking...
kernel`_cv_wait+0x125
zfs.ko`zio_wait+0x5b
zfs.ko`dmu_buf_hold_array_by_dnode+0x1dc
zfs.ko`dmu_read+0xcb
zfs.ko`zfs_freebsd_getpages+0x37b
kernel`VOP_GETPAGES_APV+0xa7
kernel`vnode_pager_getpages+0x9a
kernel`vm_fault_hold+0x885
kernel`vm_fault+0x77
kernel`trap_pfault+0x211
kernel`trap+0x506
kernel`0xffffffff806c76c2
lynxd`EVP_add_cipher+0x13
lynxd`SSL_library_init+0x11
lynxd`main+0x94
lynxd`_start+0x16f
0x2
lynxd(1925) is blocking...
kernel`_cv_wait+0x125
zfs.ko`zio_wait+0x5b
zfs.ko`dbuf_read+0x791
zfs.ko`dbuf_findbp+0x12f
zfs.ko`dbuf_hold_impl+0xa2
zfs.ko`dbuf_hold+0x1b
zfs.ko`dmu_buf_hold_array_by_dnode+0x153
zfs.ko`dmu_read_uio+0x66
zfs.ko`zfs_freebsd_read+0x3a3
kernel`VOP_READ_APV+0xa1
kernel`vn_read+0x13a
kernel`vn_io_fault+0x10b
kernel`dofileread+0x95
kernel`kern_readv+0x68
kernel`sys_read+0x63
kernel`amd64_syscall+0x343
kernel`0xffffffff806c79ab
lynxd`_read+0xa
lynxd`__srefill+0x122
lynxd`fgets+0x78
lynxd`file_gets+0x1d
lynxd`BIO_gets+0x64
lynxd`PEM_read_bio+0xf5
lynxd`PEM_X509_INFO_read_bio+0x90
lynxd`X509_load_cert_crl_file+0x47
lynxd`by_file_ctrl+0x2e
lynxd`X509_STORE_load_locations+0x4a
lynxd`sslctx_init+0x255
lynxd`main+0x215
lynxd`_start+0x16f
0x2
Requested by: gnn
Obtained from: Wheel Systems http://wheelsystems.com
af71f40a98