Date: Sat, 12 Jun 2004 12:15:21 -0700 (PDT) From: John Polstra <jdp@polstra.com> To: freebsd-arch@freebsd.org Subject: RFC: API change for sema_timedwait Message-ID: <XFMail.20040612121521.jdp@polstra.com>
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Before 5.x becomes -stable, I'd like to change the API of sema_timedwait(9). This function is used in only 3 places in the kernel, all in "dev/ips/ips_commands.c". Currently, sema_timedwait returns 0 if the operation fails due to a timeout. On success, it returns a non-zero value. This is precisely the opposite of the standard convention in the kernel, where 0 means success and a non-zero value (taken from <sys/errno.h>) means failure. The convention exists because most functions can succeed in only one way but can fail in several different ways. The reason I care about this is because I'd like to add new functions sema_wait_sig() and sema_timedwait_sig() which can be interrupted by a signal. Then sema_timedwait_sig could fail in two different ways: as a result of a timeout or as a result of a signal. If these functions returned proper errno values on failure, it would be easy to distinguish between the two failure cases. This change would also make the return values of sema_timedwait, sema_wait_sig, and sema_timedwait_sig consistent with the analogous condition variable operations cv_timedwait, cv_wait_sig, and cv_timedwait_sig and with tsleep and msleep. Does this change sound OK to you folks? John
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