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author | Srikant Patnaik | 2015-01-11 12:28:04 +0530 |
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committer | Srikant Patnaik | 2015-01-11 12:28:04 +0530 |
commit | 871480933a1c28f8a9fed4c4d34d06c439a7a422 (patch) | |
tree | 8718f573808810c2a1e8cb8fb6ac469093ca2784 /arch/tile/lib/spinlock_common.h | |
parent | 9d40ac5867b9aefe0722bc1f110b965ff294d30d (diff) | |
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Moved, renamed, and deleted files
The original directory structure was scattered and unorganized.
Changes are basically to make it look like kernel structure.
Diffstat (limited to 'arch/tile/lib/spinlock_common.h')
-rw-r--r-- | arch/tile/lib/spinlock_common.h | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/arch/tile/lib/spinlock_common.h b/arch/tile/lib/spinlock_common.h new file mode 100644 index 00000000..6ac37509 --- /dev/null +++ b/arch/tile/lib/spinlock_common.h @@ -0,0 +1,64 @@ +/* + * Copyright 2010 Tilera Corporation. All Rights Reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, version 2. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for + * more details. + * This file is included into spinlock_32.c or _64.c. + */ + +/* + * The mfspr in __spinlock_relax() is 5 or 6 cycles plus 2 for loop + * overhead. + */ +#ifdef __tilegx__ +#define CYCLES_PER_RELAX_LOOP 7 +#else +#define CYCLES_PER_RELAX_LOOP 8 +#endif + +/* + * Idle the core for CYCLES_PER_RELAX_LOOP * iterations cycles. + */ +static inline void +relax(int iterations) +{ + for (/*above*/; iterations > 0; iterations--) + __insn_mfspr(SPR_PASS); + barrier(); +} + +/* Perform bounded exponential backoff.*/ +static void delay_backoff(int iterations) +{ + u32 exponent, loops; + + /* + * 2^exponent is how many times we go around the loop, + * which takes 8 cycles. We want to start with a 16- to 31-cycle + * loop, so we need to go around minimum 2 = 2^1 times, so we + * bias the original value up by 1. + */ + exponent = iterations + 1; + + /* + * Don't allow exponent to exceed 7, so we have 128 loops, + * or 1,024 (to 2,047) cycles, as our maximum. + */ + if (exponent > 8) + exponent = 8; + + loops = 1 << exponent; + + /* Add a randomness factor so two cpus never get in lock step. */ + loops += __insn_crc32_32(stack_pointer, get_cycles_low()) & + (loops - 1); + + relax(loops); +} |