/* * arch/alpha/lib/ev6-memchr.S * * 21264 version contributed by Rick Gorton * * Finds characters in a memory area. Optimized for the Alpha: * * - memory accessed as aligned quadwords only * - uses cmpbge to compare 8 bytes in parallel * - does binary search to find 0 byte in last * quadword (HAKMEM needed 12 instructions to * do this instead of the 9 instructions that * binary search needs). * * For correctness consider that: * * - only minimum number of quadwords may be accessed * - the third argument is an unsigned long * * Much of the information about 21264 scheduling/coding comes from: * Compiler Writer's Guide for the Alpha 21264 * abbreviated as 'CWG' in other comments here * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html * Scheduling notation: * E - either cluster * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 * Try not to change the actual algorithm if possible for consistency. */ #include .set noreorder .set noat .align 4 .globl memchr .ent memchr memchr: .frame $30,0,$26,0 .prologue 0 # Hack -- if someone passes in (size_t)-1, hoping to just # search til the end of the address space, we will overflow # below when we find the address of the last byte. Given # that we will never have a 56-bit address space, cropping # the length is the easiest way to avoid trouble. zap $18, 0x80, $5 # U : Bound length beq $18, $not_found # U : ldq_u $1, 0($16) # L : load first quadword Latency=3 and $17, 0xff, $17 # E : L L U U : 00000000000000ch insbl $17, 1, $2 # U : 000000000000ch00 cmpult $18, 9, $4 # E : small (< 1 quad) string? or $2, $17, $17 # E : 000000000000chch lda $3, -1($31) # E : U L L U sll $17, 16, $2 # U : 00000000chch0000 addq $16, $5, $5 # E : Max search address or $2, $17, $17 # E : 00000000chchchch sll $17, 32, $2 # U : U L L U : chchchch00000000 or $2, $17, $17 # E : chchchchchchchch extql $1, $16, $7 # U : $7 is upper bits beq $4, $first_quad # U : ldq_u $6, -1($5) # L : L U U L : eight or less bytes to search Latency=3 extqh $6, $16, $6 # U : 2 cycle stall for $6 mov $16, $0 # E : nop # E : or $7, $6, $1 # E : L U L U $1 = quadword starting at $16 # Deal with the case where at most 8 bytes remain to be searched # in $1. E.g.: # $18 = 6 # $1 = ????c6c5c4c3c2c1 $last_quad: negq $18, $6 # E : xor $17, $1, $1 # E : srl $3, $6, $6 # U : $6 = mask of $18 bits set cmpbge $31, $1, $2 # E : L U L U nop nop and $2, $6, $2 # E : beq $2, $not_found # U : U L U L $found_it: #ifdef CONFIG_ALPHA_EV67 /* * Since we are guaranteed to have set one of the bits, we don't * have to worry about coming back with a 0x40 out of cttz... */ cttz $2, $3 # U0 : addq $0, $3, $0 # E : All done nop # E : ret # L0 : L U L U #else /* * Slow and clunky. It can probably be improved. * An exercise left for others. */ negq $2, $3 # E : and $2, $3, $2 # E : and $2, 0x0f, $1 # E : addq $0, 4, $3 # E : cmoveq $1, $3, $0 # E : Latency 2, extra map cycle nop # E : keep with cmov and $2, 0x33, $1 # E : addq $0, 2, $3 # E : U L U L : 2 cycle stall on $0 cmoveq $1, $3, $0 # E : Latency 2, extra map cycle nop # E : keep with cmov and $2, 0x55, $1 # E : addq $0, 1, $3 # E : U L U L : 2 cycle stall on $0 cmoveq $1, $3, $0 # E : Latency 2, extra map cycle nop nop ret # L0 : L U L U #endif # Deal with the case where $18 > 8 bytes remain to be # searched. $16 may not be aligned. .align 4 $first_quad: andnot $16, 0x7, $0 # E : insqh $3, $16, $2 # U : $2 = 0000ffffffffffff ($16<0:2> ff) xor $1, $17, $1 # E : or $1, $2, $1 # E : U L U L $1 = ====ffffffffffff cmpbge $31, $1, $2 # E : bne $2, $found_it # U : # At least one byte left to process. ldq $1, 8($0) # L : subq $5, 1, $18 # E : U L U L addq $0, 8, $0 # E : # Make $18 point to last quad to be accessed (the # last quad may or may not be partial). andnot $18, 0x7, $18 # E : cmpult $0, $18, $2 # E : beq $2, $final # U : U L U L # At least two quads remain to be accessed. subq $18, $0, $4 # E : $4 <- nr quads to be processed and $4, 8, $4 # E : odd number of quads? bne $4, $odd_quad_count # U : # At least three quads remain to be accessed mov $1, $4 # E : L U L U : move prefetched value to correct reg .align 4 $unrolled_loop: ldq $1, 8($0) # L : prefetch $1 xor $17, $4, $2 # E : cmpbge $31, $2, $2 # E : bne $2, $found_it # U : U L U L addq $0, 8, $0 # E : nop # E : nop # E : nop # E : $odd_quad_count: xor $17, $1, $2 # E : ldq $4, 8($0) # L : prefetch $4 cmpbge $31, $2, $2 # E : addq $0, 8, $6 # E : bne $2, $found_it # U : cmpult $6, $18, $6 # E : addq $0, 8, $0 # E : nop # E : bne $6, $unrolled_loop # U : mov $4, $1 # E : move prefetched value into $1 nop # E : nop # E : $final: subq $5, $0, $18 # E : $18 <- number of bytes left to do nop # E : nop # E : bne $18, $last_quad # U : $not_found: mov $31, $0 # E : nop # E : nop # E : ret # L0 : .end memchr EXPORT_SYMBOL(memchr) rSteven Rostedt (VMware) <rostedt@goodmis.org>2017-01-31 09:13:49 -0500 commit79c6f448c8b79c321e4a1f31f98194e4f6b6cae7 (patch) tree370efda701f03cccf21e02bb1fdd3b852547d75c /include/dt-bindings/reset/gxbb-aoclkc.h parent0c744ea4f77d72b3dcebb7a8f2684633ec79be88 (diff)
tracing: Fix hwlat kthread migration
The hwlat tracer creates a kernel thread at start of the tracer. It is pinned to a single CPU and will move to the next CPU after each period of running. If the user modifies the migration thread's affinity, it will not change after that happens. The original code created the thread at the first instance it was called, but later was changed to destroy the thread after the tracer was finished, and would not be created until the next instance of the tracer was established. The code that initialized the affinity was only called on the initial instantiation of the tracer. After that, it was not initialized, and the previous affinity did not match the current newly created one, making it appear that the user modified the thread's affinity when it did not, and the thread failed to migrate again. Cc: stable@vger.kernel.org Fixes: 0330f7aa8ee6 ("tracing: Have hwlat trace migrate across tracing_cpumask CPUs") Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'include/dt-bindings/reset/gxbb-aoclkc.h')