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[SPARC64]: Fix race in LOAD_PER_CPU_BASE()

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Since we use %g5 itself as a temporary, it can get clobbered
if we take an interrupt mid-stream and thus cause end up with
the final %g5 value too early as a result of rtrap processing.

Set %g5 at the very end, atomically, to avoid this problem.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller
2006-01-31 18:34:51 -08:00
committed by David S. Miller
parent 9954863975
commit 86b818687d
4 changed files with 18 additions and 13 deletions
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19
include/asm-sparc64/cpudata.h
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@@ -101,20 +101,25 @@ extern void setup_tba(void);
ldx [%g1 + %g6], %g6;
/* Given the current thread info pointer in %g6, load the per-cpu
* area base of the current processor into %g5. REG1 and REG2 are
* area base of the current processor into %g5. REG1, REG2, and REG3 are
* clobbered.
*
* You absolutely cannot use %g5 as a temporary in this code. The
* reason is that traps can happen during execution, and return from
* trap will load the fully resolved %g5 per-cpu base. This can corrupt
* the calculations done by the macro mid-stream.
*/
#ifdef CONFIG_SMP
#define LOAD_PER_CPU_BASE(REG1, REG2) \
#define LOAD_PER_CPU_BASE(REG1, REG2, REG3) \
ldub [%g6 + TI_CPU], REG1; \
sethi %hi(__per_cpu_shift), %g5; \
sethi %hi(__per_cpu_shift), REG3; \
sethi %hi(__per_cpu_base), REG2; \
ldx [%g5 + %lo(__per_cpu_shift)], %g5; \
ldx [REG3 + %lo(__per_cpu_shift)], REG3; \
ldx [REG2 + %lo(__per_cpu_base)], REG2; \
sllx REG1, %g5, %g5; \
add %g5, REG2, %g5;
sllx REG1, REG3, REG3; \
add REG3, REG2, %g5;
#else
#define LOAD_PER_CPU_BASE(REG1, REG2)
#define LOAD_PER_CPU_BASE(REG1, REG2, REG3)
#endif
#endif /* _SPARC64_CPUDATA_H */