Adding upstream version 4.22.0.upstream/4.22.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 63 insertions, 0 deletions

diff --git a/upstream/mageia-cauldron/man9/save_flags.9 b/upstream/mageia-cauldron/man9/save_flags.9
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+.\" -*- nroff -*-
+.TH save_flags 9 "$Date:$" "Linux DDI" "Linux Kernel Functions"
+.SH NAME
+save_flags, restore_flags \- save/restore processor state and irq mask
+.SH SYNOPSIS
+.B #include <asm/system.h>
+.sp
+.BI "unsigned long " flags ";"
+.br
+.BI "void save_flags(" flags ")"
+.br
+.BI "void restore_flags(" flags ")"
+.SH DESCRIPTION
+The
+.B save_flags
+and
+.B restore_flags
+macros cooperate with the
+.B cli
+function to provide interrupt protection to critical sections of
+code. The
+.B save_flags
+function saves the current processor state, most specifically the
+interrupt priority level, in the
+.I flags
+value (which must be an l-value). The flags must be passed to a
+subsequent call to
+.B restore_flags
+to restore the processor state.
+.PP
+The
+.B save_flags
+macro does not affect the processor state, but drivers may use the
+.BR cli (9)
+and
+.B sti
+functions to disable and enable interrupts after saving the current
+flags. When the critical section of code is passed, the
+.B restore_flags
+returns the processor to its state at the point where the matching
+.B save_flags
+was called.
+.PP
+Only values returned by
+.B save_flags
+can be passed to
+.B restore_flags.
+Any other values may cause unpredictable results, and are
+certainly not portable.
+.SH "RETURN VALUE"
+The
+.B restore_flags
+macro saves the processor state in the
+.I flags
+parameter, which must be a non-const l-value.
+.SH AVAILABILITY
+Linux 1.0+
+.SH "SEE ALSO"
+.BR "cli" (9)
+.SH AUTHOR
+Stephen Williams (steve@icarus.com)
+.SH BUGS
+How does all this react with symmetric multiprocessor machines?