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diff --git a/upstream/mageia-cauldron/man9/init_bh.9 b/upstream/mageia-cauldron/man9/init_bh.9 new file mode 100644 index 00000000..9a1aac8a --- /dev/null +++ b/upstream/mageia-cauldron/man9/init_bh.9 @@ -0,0 +1,188 @@ +.\" -*- nroff -*- +.TH INIT_BH 9 "1997/08/14 07:53:12" "Linux DDI 2.1.48" "Linux Kernel Functions" +.\" copyright (C) 1997 Neil Moore <amethyst@maxwell.ml.org> +.\" +.\" Permission is granted to make and distribute verbatim copies of this +.\" manual provided the copyright notice and this permission notice are +.\" preserved on all copies. +.\" +.\" Permission is granted to copy and distribute modified versions of this +.\" manual under the conditions for verbatim copying, provided that the +.\" entire resulting derived work is distributed under the terms of a +.\" permission notice identical to this one +.\" +.\" Since the Linux kernel and libraries are constantly changing, this +.\" manual page may be incorrect or out-of-date. The author(s) assume no +.\" responsibility for errors or omissions, or for damages resulting from +.\" the use of the information contained herein. The author(s) may not +.\" have taken the same level of care in the production of this manual, +.\" which is licensed free of charge, as they might when working +.\" professionally. +.\" +.\" Formatted or processed versions of this manual, if unaccompanied by +.\" the source, must acknowledge the copyright and authors of this work. + +.\" Turn off hyphentation +.hlm 0 +.\" Turn off adjustment +.na +.SH NAME +init_bh, remove_bh, mark_bh, disable_bh, enable_bh \- split-half interrupt handling +.SH SYNOPSIS +.B #include <linux/interrupt.h> +.\" To keep all components of a declaration together, escape all white +.\" space except after a comma. In case the proc name plus the first +.\" declaration is too long for one line, allow a break after '(' by +.\" adding '\%'. +.HP +.BI "void\ init_bh(int " nr ", void\ (*" routine ")(void));" +.\" We don't want an inter-paragraph space between the two declarations, +.\" but we have to end the paragraph to stop the hanging indent. .PD 0 +.\" gets rid of inter-paragraph spacing +.PD 0 +.HP +.BI "void\ remove_bh(int\ " nr ");" +.HP +.BI "void\ mark_bh(int\ " nr ");" +.HP +.BI "void\ disable_bh(int\ " nr ");" +.HP +.BI "void\ enable_bh(int\ " nr ");" +.\" And set it back to normal now +.PD 1 +.\" Back to standard adjustment +.ad +.\" Allow hypenation, omit if you want no hyphenation in the man page +.hlm 1 +.SH DESCRIPTION +.SS Theory +.PP +Split-half handling is a means of dividing an interrupt handler into two +sections, one of which (known as the \(oqtop half') is time-critical and +one of which (the \(oqbottom half') is not. +.PP +The top half (the handler registered with +.BR "request_irq" "(9))" +normally moves data between the device and a memory buffer, ensures that the +device is in a sane state, and little else. While the top half of a handler +is running, the IRQ is question is blocked; if it is a fast interrupt handler +(i.e., it has +.B SA_INTERRUPT +set), all interrupts are disabled. +.PP +The bottom half does whatever remains to be done. Bottom halves run with +interrupts enabled, although a locking mechanism ensures that only one +bottom half will be running at a given time. Bottom halves are run by +.BR do_bottom_half() , +which is called from +.B schedule() +and +.BR ret_from_sys_call() ". " +.SS Usage +.PP +.B init_bh() +installs +.I routine() +as bottom half number +.IR nr ". " +It operates by adding an entry to the +.B bh_base[] +table, and setting the appropriate bit of the +.B bh_mask +vector. Rather than specifying a number explicitly, one should add an entry +to the anonymous enum in +.IR "include/linux/interrupt.h" ". " +.PP +.B remove_bh() +removes bottom half number +.I nr +from the list of bottom halves. It removes the entry from +.B bh_base[] +and clears the appropriate bit of +.BR bh_mask ". " +.PP +.B mark_bh() +requests that the kernel run the specified bottom half at the first available +opportunity. This function is normally called from the top half of an interrupt +handler. It operates by setting the appropriate bit of the +.B bh_active +vector. +.PP +.B disable_bh() +disables bottom half number +.I nr +by clearing the appropriate bit of +.BR bh_mask . +This function also increments +.BI bh_mask_count[ nr ]\fR, +which is used to ensure that nested calls to +.B disable_bh() +must be matched by an equal number of calls to +.BR enable_bh() . +.PP +.B enable_bh() +enables a bottom half previously disabled by +.BR disable_bh() . +This function decrements +.BI bh_mask_count[ nr ]\fR. +Then, if that value is zero, the specified bottom half is enabled +by setting the appropriate bit of +.BR bh_mask . +.SH "RETURN VALUE" +No value is returned. +.SH AVAILABILITY +Linux 2.0+. +.B init_bh() +and +.B remove_bh() +were not present in older versions on Linux. Under those versions, +.B bh_base[] +and +.B bh_mask +must be modified by hand. +.SH "SEE ALSO" +.BR request_irq "(9), " queue_task "(9)" +.PP +.IR include/asm*/softirq.h ", " include/linux/interrupt.h ", " kernel/softirq.c +.PP +\(lqKernel Korner\(rq in issue 26 of +.I The Linux Journal +includes a discussion of split-half interrupts under Linux. An online copy of +this article can be found at +.BR http://www.ssc.com/lj/issue26/interrupt.html . +.SH AUTHOR +.RI "Neil Moore <" amethyst@maxwell.ml.org ">" +.SH BUGS +Only 32 bottom halves are allowed. Increasing this number requires changing +the size of +.B bh_base[] +and +.BI bh_mask_count[] +in +.IR kernel/softirq.c, +and changing +.B bh_active +and +.B bh_mask +(in the same file) to a larger type. A better solution, however, would be to +consolidate multiple bottom halves into a single one by using task queues. +See +.BR queue_task (9) +for details. +.\" +.\" init_bh.9,v +.\" Revision 1.4 1997/08/14 07:53:12 amethyst +.\" Formatting changes. +.\" +.\" Revision 1.3 1997/08/08 16:40:50 amethyst +.\" Updated for 2.1.48 -- init_bh() and friends are now available again on the PPC. +.\" +.\" Revision 1.2 1997/07/27 09:39:45 amethyst +.\" Changed some wording. +.\" Fixed a few typographical warts. +.\" Added email address to copyright notice. +.\" +.\" Revision 1.1 1997/07/27 09:27:17 amethyst +.\" Initial revision +.\" +.\" |