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freebsd/lib/libpmc/pmc_read.3
Ulrich Spörlein aa12cea2cc mdoc: order prologue macros consistently by Dd/Dt/Os
Although groff_mdoc(7) gives another impression, this is the ordering
most widely used and also required by mdocml/mandoc.

Reviewed by:	ru
Approved by:	philip, ed (mentors)
2010-04-14 19:08:06 +00:00

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.\" Copyright (c) 2007 Joseph Koshy. All rights reserved.
.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\"
.\" This software is provided by Joseph Koshy ``as is'' and
.\" any express or implied warranties, including, but not limited to, the
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.\" $FreeBSD$
.\"
.Dd November 25, 2007
.Dt PMC_READ 3
.Os
.Sh NAME
.Nm pmc_read ,
.Nm pmc_rw ,
.Nm pmc_write ,
.Nd read and write hardware performance counters
.Sh LIBRARY
.Lb libpmc
.Sh SYNOPSIS
.In pmc.h
.Ft int
.Fn pmc_read "pmc_id_t pmc" "pmc_value_t *value"
.Ft int
.Fn pmc_rw "pmc_id_t pmc" "pmc_value_t newvalue" "pmc_value_t *oldvaluep"
.Ft int
.Fn pmc_write "pmc_id_t pmc" "pmc_value_t value"
.Sh DESCRIPTION
These functions read and write the current value of a PMC.
.Pp
Function
.Fn pmc_read
with read the current value of the PMC specified by argument
.Fa pmc
and write it to the location specified by argument
.Fa value .
.Pp
Function
.Fn pmc_write
will set the current value of the PMC specified by argument
.Fa pmc
to the value specified by argument
.Fa value .
.Pp
Function
.Fn pmc_rw
combines a read and a write into a single atomic operation.
.Pp
For write operations the PMC should be a quiescent state.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
A call to these functions may fail with the following errors:
.Bl -tag -width Er
.It Bq Er EBUSY
A write operation specified a currently running PMC.
.It Bq Er EINVAL
Argument
.Fa pmc
specified a PMC not in a readable state.
.It Bq Er EINVAL
The PMC specified by argument
.Fa pmc
was not owned by the current process.
.El
.Sh SEE ALSO
.Xr pmc 3 ,
.Xr hwpmc 4