.TH "__test_and_set_bit" 9 "__test_and_set_bit" "25 May 1998" "Kernel Hacker's Manual" LINUX
.SH NAME
__test_and_set_bit \-  Set a bit and return its old value
.SH SYNOPSIS
.B "int" __test_and_set_bit
.BI "(int " nr ","
.BI "volatile void *" addr ");"
.SH ARGUMENTS
.IP "nr" 12
 Bit to set
.IP "addr" 12
 Address to count from
.SH "DESCRIPTION"
This operation is non-atomic and can be reordered.  
If two examples of this operation race, one can appear to succeed
but actually fail.  You must protect multiple accesses with a lock.