Date: Thu, 6 May 1999 22:31:35 -0700 (PDT) From: "Sameer R. Manek" <manek@ecst.csuchico.edu> To: freebsd-questions@freebsd.org, freebsd-hackers@freebsd.org Subject: bug with lockf(3)? Message-ID: <Pine.GHP.4.05.9905062228500.7884-100000@polio.ecst.csuchico.edu>
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I had posted this originally to freebsd-stable but didn't get any response
from that list.
On freebsd 3-1-stable I'm not sure if this is a bug or my misinterpetation
of how lockf() works. But here's the situation.
Given 2 processes A and B, both with open file descriptors to a file,
using open ("file.txt",O_RDWR)
A calls lockf (fd,F_LOCK,0) and proceeds to read/write to file
while file is still locked....including using lseek to jump to the
begining of the file
B calls lockf (fd,F_LOCK,0) and enters blocked state
A calls lockf (fd,F_ULOCK,0)
B is still in blocked state, until A exit(3)s.
According to the man page:
F_LOCK and F_TLOCK requests differ only by the action taken if the
section is not available. F_LOCK blocks the calling process until the
section is available. F_TLOCK makes the function fail if the section is
already locked by another process.
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Sameer Manek manek@ecst.csuchico.edu
"They that will sacrifice liberty in exchange for temporary safety
deserve neither liberty or safety." -Ben Franklin
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