[Linux-ia64] Replacements for local_irq_xxx()

Keith Owens
2001-05-10T08:55:13Z

Existing local_irq_xxx() routines clear psr.i which masks all
interrupts, including NMI. Then the only way to get the attention of a
cpu in a disabled spin loop is via INIT which is too drastic. How
about these alternatives which set cr.tpr.mmi instead, masking all
external interrupts except NMI?

This is not complete, I have to do the debugging versions plus check
out callers of ia64_{get,set}_tpr and resolve any conflicts. Before I
do any more work, is it worth continuing with this or do we live with
psr.i and accept that the only remedy for a cpu that is hung in a
disabled spin loop is to reboot the entire machine?

/* Nothing changes cr.tpr except local_irq_xxx() and they should always
* leave tpr in the same state that they found it, so there is no need
* to serialize access to tpr. If this is incorrect, uncomment the
* references to psr and the following srlz.d and add r15 to the clobbers.
*/

# define local_irq_save(x) \
do { \
__asm__ __volatile__ ( \
";;\n\t" \
"# mov r15=psr;\n\t" \
"mov r17=(1 << 16);\n\t" \
"# ;; rsm psr.i;;\n\t" \
"mov %0=cr.tpr;;\n\t" \
"or r17=r17,%0;;\n\t" \
"mov cr.tpr=r17;;\n\t" \
"srlz.d;;\n\t" \
"# mov psr.l=r15;;\n\t" \
"# srlz.d;;\n\t" \
: "=r" (x) : : "r16", "r17"); \
} while (0)

# define local_irq_disable() \
do { \
__asm__ __volatile__ ( \
";;\n\t" \
"# mov r15=psr;\n\t" \
"mov r17=(1 << 16);\n\t" \
"# ;; rsm psr.i;;\n\t" \
"mov r16=cr.tpr;;\n\t" \
"or r17=r17,r16;;\n\t" \
"mov cr.tpr=r17;;\n\t" \
"srlz.d;;\n\t" \
"# mov psr.l=r15;;\n\t" \
"# srlz.d;;\n\t" \
: : : "r16", "r17"); \
} while (0)

# define local_irq_restore(x) \
do { \
__asm__ __volatile__ ( \
";;\n\t" \
"# mov r15=psr;\n\t" \
"# rsm psr.i;;\n\t" \
"mov cr.tpr=%0;;\n\t" \
"srlz.d;;\n\t" \
"# mov psr.l=r15;;\n\t" \
"# srlz.d;;\n\t" \
: : "r" (x) ); \
} while (0)