libvirt/examples/systemtap/lock-debug.stp

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#!/usr/bin/stap --ldd -d /usr/sbin/libvirtd -c libvirtd
#
# Usage with installed libvirt daemon:
# stap --ldd -d /usr/sbin/libvirtd -c libvirtd \
# lock-debug.stp /usr/lib/libvirt.so
#
# If made executable; simple './lock-debug.stp' should work too.
#
# TODOs:
#
# Document usage with uninstalled daemon and libs. Assuming CWD is toplevel
# source git directory, it should be only slight modification to the following:
#
# ./run stap --ldd -c daemon/libvirtd -d daemon/libvirtd
# examples/systemtap/lock-debug.stp src/.libs/libvirt.so
#
# Debug RWLock mechanisms as well.
#
# Author: Martin Kletzander <mkletzan@redhat.com>
global mx_tolock
global mx_locked
function filter()
{
if (pid() != target())
return 1
return 0
}
probe library = process( %( $# > 0 %? @1 %: "/usr/lib/libvirt.so" %) )
{
if (filter()) next
}
probe lock = library.function("virMutexLock")
{
lockname = usymdata($m)
}
probe unlock = library.function("virMutexUnlock")
{
lockname = usymdata($m)
}
probe begin
{
%( $# > 1 %? println("error: Too many parameters"); exit();
%: print("Started, press ^C when the process hangs\n"); %)
}
probe lock.call
{
mx_tolock[lockname, tid()] = sprint_usyms(ubacktrace())
}
probe lock.return
{
if ([lockname, tid()] in mx_tolock) {
mx_locked[lockname, tid()] = mx_tolock[lockname, tid()]
delete mx_tolock[lockname, tid()]
} else {
printf("internal error: lock acquired unwillingly?\n")
}
}
probe unlock.call
{
found = 0
foreach ([lock, tid] in mx_locked) {
if (lock != lockname)
continue
if (tid != tid()) {
printf("Warning: lock released on different thread that locked it.\n")
printf("Lock trace:\n%s\n", mx_locked[lock, tid])
printf("Unlock trace:\n%s\n", sprint_usyms(ubacktrace()))
}
found = tid
break
}
if (found && [lockname, found] in mx_locked)
delete mx_locked[lockname, found]
}
probe end
{
tmp = 0
printf("\n=============\n")
foreach (bt1 = [lock1, tid1] in mx_tolock) {
deadlock = 0
foreach (bt2 = [lock2, tid2] in mx_tolock) {
if (lock1 == lock2) {
if (!tmp++)
printf("The following locks cannot be acquired:\n")
if (!deadlock++)
printf("Lock %s was locked in thread %d with this trace:\n%s\n",
lock1, tid1, bt1)
printf("and is waiting to be locked by thread %d here:\n%s\n",
tid2, bt2)
}
}
if (deadlock)
printf("---\n")
}
if (!tmp)
printf("No deadlocks found, sorry.\n")
}