diff options
| -rw-r--r-- | ChangeLog.txt | 4 | ||||
| -rw-r--r-- | ports/linux/guts/openat.c | 37 |
2 files changed, 41 insertions, 0 deletions
diff --git a/ChangeLog.txt b/ChangeLog.txt index f79c2d1..b5f64c7 100644 --- a/ChangeLog.txt +++ b/ChangeLog.txt @@ -1,3 +1,7 @@ +2019-04-10: + * (seebs) Experimental workaround for special non-blocking open + case. + 2019-04-09: * (seebs) Partial fix for db corruption issue. * (seebs) Make a glibc renameat2 wrapper that just fails because diff --git a/ports/linux/guts/openat.c b/ports/linux/guts/openat.c index 924e354..cc6b118 100644 --- a/ports/linux/guts/openat.c +++ b/ports/linux/guts/openat.c @@ -7,8 +7,10 @@ * int rc = -1; */ struct stat64 buf; + int overly_magic_nonblocking = 0; int existed = 1; int save_errno; + sigset_t local_saved_sigmask; /* mask out mode bits appropriately */ mode = mode & ~pseudo_umask; @@ -61,6 +63,27 @@ errno = save_errno; } + /* if a pipe is opened without O_NONBLOCK, for only reading or + * only writing, it can block forever. We need to do extra magic + * in that case... + */ + if (!(flags & O_NONBLOCK) && ((flags & (O_WRONLY | O_RDONLY | O_RDWR)) != O_RDWR)) { + save_errno = errno; +#ifdef PSEUDO_NO_REAL_AT_FUNCTIONS + rc = real___xstat64(_STAT_VER, path, &buf); +#else + rc = real___fxstatat64(_STAT_VER, dirfd, path, &buf, 0); +#endif + if (rc != -1 && S_ISFIFO(buf.st_mode)) { + overly_magic_nonblocking = 1; + } + } + + /* this is a horrible special case and i do not know whether it will work */ + if (overly_magic_nonblocking) { + pseudo_droplock(); + sigprocmask(SIG_SETMASK, &pseudo_saved_sigmask, &local_saved_sigmask); + } /* because we are not actually root, secretly mask in 0600 to the * underlying mode. The ", 0" is because the only time mode matters * is if a file is going to be created, in which case it's @@ -71,6 +94,20 @@ #else rc = real_openat(dirfd, path, flags, PSEUDO_FS_MODE(mode, 0)); #endif + if (overly_magic_nonblocking) { + save_errno = errno; + sigprocmask(SIG_SETMASK, &local_saved_sigmask, NULL); + /* well this is a problem. we can't NOT proceed; we may have + * already opened the file! we can't even return up the call + * stack to stuff that's going to try to drop the lock. + */ + if (pseudo_getlock()) { + pseudo_diag("PANIC: after opening a readonly/writeonly FIFO (path '%s', fd %d, errno %d, saved errno %d), could not regain lock. unrecoverable. sorry. bye.\n", + path, rc, errno, save_errno); + abort(); + } + errno = save_errno; + } if (rc != -1) { save_errno = errno; |