Messages in this thread |  | | Date | Fri, 2 Feb 2007 14:28:23 -0500 | From | "Aaron Wiebe" <> | Subject | Fwd: uninterruptable fcntl calls |
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Greetings,
I've run into a situation where fcntl F_SETLKW calls lock up nearly completely. I've tried several approaches to handle this case, and have yet to come up with some method of handling this. I've never really ventured outside userspace, so I'm turning to this list to try and get a handle on this.
Over NFSv3 udp, this situation takes place VERY rarely, however with the volume I do, its creating a problem.
In short, I am attempting to read or write lock, and the call hangs to the point where a sigkill is not captured - no signal is. I've tried alarming out and I've tried switching the socket to nonblocking - nothing I can think of prevents or even allows me to handle the case. I understand NFS locking can be rather sketchy at times - but all I need is the ability to handle the case.
I can force the process to die by sending a sigkill, then stracing. The strace reports the process as sigstop, then processes the kill signal.
All I need here is a method of capturing this case. I can "repair" the stuck lock by regenerating the file, but I can't capture the case in order to handle this in code.
Any help would be useful - I am currently running 2.6.15.6 compiled with the NFS patches from linux-nfs.org, but this case was happening before applying those patches. I'd be happy to provide any more information nessecary. I've been struggling with this one for a few months now.
Thanks, -Aaron
Straces:
rt_sigaction(SIGALRM, {0xb7f56640, [ALRM], 0}, {SIG_DFL}, 8) = 0 alarm(120) = 0 fcntl64(3, F_SETLKW, {type=F_RDLCK, whence=SEEK_SET, start=0, len=0} [hangs]
Or:
fcntl64(3, F_GETFL) = 0x8002 (flags O_RDWR|O_LARGEFILE) fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK|O_LARGEFILE) = 0 fcntl64(3, F_SETLKW, {type=F_RDLCK, whence=SEEK_SET, start=0, len=0}
Code used for locking:
static int db_lock(int fd, int type) { struct flock fl; struct timespec *tv = (struct timespec *) malloc(sizeof(struct timespec)); int ret, c = 0;
if(!(fd > 0)) return -1;
#ifdef SIGALRM_HACK /* after two minutes, wig out */ sigalrm_set(); alarm(120); #endif
fl.l_whence = SEEK_SET; fl.l_start = 0; fl.l_len = 0; fl.l_type = type;
#ifdef NONBLOCKING_HACK set_nonblocking(fd); #endif
while((ret = fcntl(fd, F_SETLKW, &fl)) < 0) { c++; if(c > 600) { /* we've been waiting for 60 seconds... */ my_error("stuck on fcntl request, aborting"); return -1; } tv->tv_nsec = 100; /* 10th of a second wait */ tv->tv_sec = 0; nanosleep(tv, NULL); } free(tv); #ifdef SIGALRM_HACK sigalrm_unset(); #endif #ifdef NONBLOCKING_HACK unset_nonblocking(fd); #endif return ret; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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