Add a little, but very useful script for use with programs that work using an
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