Re: [libvirt] [PATCH] Avoid deadlock on logging mutex due to fork in virFileCreate/virDirCreate.

On Wed, Feb 03, 2010 at 10:27:32AM -0500, Laine Stump wrote: > These functions have the same potential problem that Cole found in > virExec - if the log mutex is currently held at the time of the fork, > the child process' logging mutex will be locked, but nobody in the > process to unlock it. If the child process tries to log anything, it > will wait forever for this lock. The solution is to have the parent > acquire the lock before fork, then both parent and child release the > lock right after. > > Note that this patch requires Cole's patch to be applied first. > --- > src/util/util.c | 12 ++++++++++-- > 1 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/src/util/util.c b/src/util/util.c > index 901c0d2..d8a2394 100644 > --- a/src/util/util.c > +++ b/src/util/util.c > @@ -1263,7 +1263,11 @@ int virFileCreate(const char *path, mode_t mode, > * following dance avoids problems caused by root-squashing > * NFS servers. */ > > - if ((pid = fork())< 0) { > + virLogLock(); > + pid = fork(); > + virLogUnlock(); > + > + if (pid< 0) { > ret = errno; > virReportSystemError(NULL, errno, > _("cannot fork o create file '%s'"), path); > @@ -1369,7 +1373,11 @@ int virDirCreate(const char *path, mode_t mode, > return virDirCreateSimple(path, mode, uid, gid, flags); > } > > - if ((pid = fork())< 0) { > + virLogLock(); > + pid = fork(); > + virLogUnlock(); > + > + if (pid< 0) { > ret = errno; > virReportSystemError(NULL, errno, > _("cannot fork to create directory '%s'"), > Okay, makes sense, ACK, and applied ! Maybe at some point a wrapper around fork() may be nicer.