'\" t
.\"     Title: rcu_read_lock_held
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: Driver Basics
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "RCU_READ_LOCK_HELD" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Driver Basics"
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.SH "NAME"
rcu_read_lock_held \- might we be in RCU read\-side critical section?
.SH "SYNOPSIS"
.HP \w'int\ rcu_read_lock_held('u
.BI "int rcu_read_lock_held(" "void" ");"
.SH "ARGUMENTS"
.PP
\fIvoid\fR
.RS 4
no arguments
.RE
.SH "DESCRIPTION"
.PP
.PP
If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU read\-side critical section\&. In absence of CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU read\-side critical section unless it can prove otherwise\&. This is useful for debug checks in functions that require that they be called within an RCU read\-side critical section\&.
.PP
Checks
\fBdebug_lockdep_rcu_enabled\fR
to prevent false positives during boot and while lockdep is disabled\&.
.PP
Note that
\fBrcu_read_lock\fR
and the matching
\fBrcu_read_unlock\fR
must occur in the same context, for example, it is illegal to invoke
\fBrcu_read_unlock\fR
in process context if the matching
\fBrcu_read_lock\fR
was invoked from within an irq handler\&.
.PP
Note that
\fBrcu_read_lock\fR
is disallowed if the CPU is either idle or offline from an RCU perspective, so check for those as well\&.
.SH "COPYRIGHT"
.br