57 lines
1.2 KiB
Text
57 lines
1.2 KiB
Text
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.TH SPLHI 9
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.SH NAME
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splhi, spllo, splx, islo \- enable and disable interrupts
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.SH SYNOPSIS
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.ta \w'\fLvoid 'u
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.B
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int spllo(void)
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.PP
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.B
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int splhi(void)
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.PP
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.B
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void splx(int x)
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.PP
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.B
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int islo(void)
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.SH DESCRIPTION
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These primitives enable and disable maskable interrupts on the current
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processor.
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Generally, device drivers should use
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.I ilock
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(see
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.IR lock (9)),
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.IR sleep (9),
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or the functions in
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.IR qio (9)
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to control interaction between processes and interrupt handlers.
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Those routines (but not these) provide correct synchronisation on multiprocessors.
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.PP
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.I Spllo
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enables interrupts and returns a flag representing the previous interrupt enable state.
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It must not normally be called from interrupt level.
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.PP
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.I Splhi
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disables all maskable interrupts and returns the previous interrupt enable state.
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The period during which interrupts are disabled had best be short,
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or real-time applications will suffer.
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.PP
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.I Splx
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restores the interrupt enable state to
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.IR x ,
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which must be a value returned
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by a previous call to
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.I splhi
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or
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.IR spllo .
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.PP
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.I Islo
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returns true (non-zero) if interrupts are currently enabled, and 0 otherwise.
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.SH SOURCE
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.B /sys/src/9/*/l.s
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.SH SEE ALSO
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.IR lock (9),
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.IR qio (9),
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.IR sleep (9),
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.IR intrenable (9)
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