/*++ /* NAME /* deliver_flock 3 /* SUMMARY /* lock open file for mail delivery /* SYNOPSIS /* #include <deliver_flock.h> /* /* int deliver_flock(fd, lock_style, why) /* int fd; /* int lock_style; /* VSTRING *why; /* DESCRIPTION /* deliver_flock() sets one exclusive kernel lock on an open file, /* for example in order to deliver mail. /* It performs several non-blocking attempts to acquire an exclusive /* lock before giving up. /* /* Arguments: /* .IP fd /* A file descriptor that is associated with an open file. /* .IP lock_style /* A locking style defined in myflock(3). /* .IP why /* A null pointer, or storage for diagnostics. /* DIAGNOSTICS /* deliver_flock() returns -1 in case of problems, 0 in case /* of success. The reason for failure is returned via the \fIwhy\fR /* parameter. /* CONFIGURATION PARAMETERS /* deliver_lock_attempts, number of locking attempts /* deliver_lock_delay, time in seconds between attempts /* sun_mailtool_compatibility, disable kernel locking /* LICENSE /* .ad /* .fi /* The Secure Mailer license must be distributed with this software. /* AUTHOR(S) /* Wietse Venema /* IBM T.J. Watson Research /* P.O. Box 704 /* Yorktown Heights, NY 10598, USA /*--*/ /* System library. */ #include "sys_defs.h" #include <unistd.h> /* Utility library. */ #include <vstring.h> #include <myflock.h> #include <iostuff.h> /* Global library. */ #include "mail_params.h" #include "deliver_flock.h" /* Application-specific. */ #define MILLION 1000000 /* deliver_flock - lock open file for mail delivery */ int deliver_flock(int fd, int lock_style, VSTRING *why) { int i; for (i = 1; /* void */ ; i++) { if (myflock(fd, lock_style, MYFLOCK_OP_EXCLUSIVE | MYFLOCK_OP_NOWAIT) == 0) return (0); if (i >= var_flock_tries) break; rand_sleep(var_flock_delay * MILLION, var_flock_delay * MILLION / 2); } if (why) vstring_sprintf(why, "unable to lock for exclusive access: %m"); return (-1); }