3.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Guy Martin <gmsoft@xxxxxxxxxxxx> commit 89206491201cbd1571009b36292af781cef74c1b upstream. The current LWS cas only works correctly for 32bit. The new LWS allows for CAS operations of variable size. Signed-off-by: Guy Martin <gmsoft@xxxxxxxxxxxx> Signed-off-by: Helge Deller <deller@xxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/parisc/kernel/syscall.S | 233 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 229 insertions(+), 4 deletions(-) --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -74,7 +74,7 @@ ENTRY(linux_gateway_page) /* ADDRESS 0xb0 to 0xb8, lws uses two insns for entry */ /* Light-weight-syscall entry must always be located at 0xb0 */ /* WARNING: Keep this number updated with table size changes */ -#define __NR_lws_entries (2) +#define __NR_lws_entries (3) lws_entry: gate lws_start, %r0 /* increase privilege */ @@ -502,7 +502,7 @@ lws_exit: /*************************************************** - Implementing CAS as an atomic operation: + Implementing 32bit CAS as an atomic operation: %r26 - Address to examine %r25 - Old value to check (old) @@ -659,6 +659,230 @@ cas_action: ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 3b-linux_gateway_page) + /*************************************************** + New CAS implementation which uses pointers and variable size + information. The value pointed by old and new MUST NOT change + while performing CAS. The lock only protect the value at %r26. + + %r26 - Address to examine + %r25 - Pointer to the value to check (old) + %r24 - Pointer to the value to set (new) + %r23 - Size of the variable (0/1/2/3 for 8/16/32/64 bit) + %r28 - Return non-zero on failure + %r21 - Kernel error code + + %r21 has the following meanings: + + EAGAIN - CAS is busy, ldcw failed, try again. + EFAULT - Read or write failed. + + Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only) + + ****************************************************/ + + /* ELF32 Process entry path */ +lws_compare_and_swap_2: +#ifdef CONFIG_64BIT + /* Clip the input registers */ + depdi 0, 31, 32, %r26 + depdi 0, 31, 32, %r25 + depdi 0, 31, 32, %r24 + depdi 0, 31, 32, %r23 +#endif + + /* Check the validity of the size pointer */ + subi,>>= 4, %r23, %r0 + b,n lws_exit_nosys + + /* Jump to the functions which will load the old and new values into + registers depending on the their size */ + shlw %r23, 2, %r29 + blr %r29, %r0 + nop + + /* 8bit load */ +4: ldb 0(%sr3,%r25), %r25 + b cas2_lock_start +5: ldb 0(%sr3,%r24), %r24 + nop + nop + nop + nop + nop + + /* 16bit load */ +6: ldh 0(%sr3,%r25), %r25 + b cas2_lock_start +7: ldh 0(%sr3,%r24), %r24 + nop + nop + nop + nop + nop + + /* 32bit load */ +8: ldw 0(%sr3,%r25), %r25 + b cas2_lock_start +9: ldw 0(%sr3,%r24), %r24 + nop + nop + nop + nop + nop + + /* 64bit load */ +#ifdef CONFIG_64BIT +10: ldd 0(%sr3,%r25), %r25 +11: ldd 0(%sr3,%r24), %r24 +#else + /* Load new value into r22/r23 - high/low */ +10: ldw 0(%sr3,%r25), %r22 +11: ldw 4(%sr3,%r25), %r23 + /* Load new value into fr4 for atomic store later */ +12: flddx 0(%sr3,%r24), %fr4 +#endif + +cas2_lock_start: + /* Load start of lock table */ + ldil L%lws_lock_start, %r20 + ldo R%lws_lock_start(%r20), %r28 + + /* Extract four bits from r26 and hash lock (Bits 4-7) */ + extru %r26, 27, 4, %r20 + + /* Find lock to use, the hash is either one of 0 to + 15, multiplied by 16 (keep it 16-byte aligned) + and add to the lock table offset. */ + shlw %r20, 4, %r20 + add %r20, %r28, %r20 + + rsm PSW_SM_I, %r0 /* Disable interrupts */ + /* COW breaks can cause contention on UP systems */ + LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */ + cmpb,<>,n %r0, %r28, cas2_action /* Did we get it? */ +cas2_wouldblock: + ldo 2(%r0), %r28 /* 2nd case */ + ssm PSW_SM_I, %r0 + b lws_exit /* Contended... */ + ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ + + /* + prev = *addr; + if ( prev == old ) + *addr = new; + return prev; + */ + + /* NOTES: + This all works becuse intr_do_signal + and schedule both check the return iasq + and see that we are on the kernel page + so this process is never scheduled off + or is ever sent any signal of any sort, + thus it is wholly atomic from usrspaces + perspective + */ +cas2_action: + /* Jump to the correct function */ + blr %r29, %r0 + /* Set %r28 as non-zero for now */ + ldo 1(%r0),%r28 + + /* 8bit CAS */ +13: ldb,ma 0(%sr3,%r26), %r29 + sub,= %r29, %r25, %r0 + b,n cas2_end +14: stb,ma %r24, 0(%sr3,%r26) + b cas2_end + copy %r0, %r28 + nop + nop + + /* 16bit CAS */ +15: ldh,ma 0(%sr3,%r26), %r29 + sub,= %r29, %r25, %r0 + b,n cas2_end +16: sth,ma %r24, 0(%sr3,%r26) + b cas2_end + copy %r0, %r28 + nop + nop + + /* 32bit CAS */ +17: ldw,ma 0(%sr3,%r26), %r29 + sub,= %r29, %r25, %r0 + b,n cas2_end +18: stw,ma %r24, 0(%sr3,%r26) + b cas2_end + copy %r0, %r28 + nop + nop + + /* 64bit CAS */ +#ifdef CONFIG_64BIT +19: ldd,ma 0(%sr3,%r26), %r29 + sub,= %r29, %r25, %r0 + b,n cas2_end +20: std,ma %r24, 0(%sr3,%r26) + copy %r0, %r28 +#else + /* Compare first word */ +19: ldw,ma 0(%sr3,%r26), %r29 + sub,= %r29, %r22, %r0 + b,n cas2_end + /* Compare second word */ +20: ldw,ma 4(%sr3,%r26), %r29 + sub,= %r29, %r23, %r0 + b,n cas2_end + /* Perform the store */ +21: fstdx %fr4, 0(%sr3,%r26) + copy %r0, %r28 +#endif + +cas2_end: + /* Free lock */ + stw,ma %r20, 0(%sr2,%r20) + /* Enable interrupts */ + ssm PSW_SM_I, %r0 + /* Return to userspace, set no error */ + b lws_exit + copy %r0, %r21 + +22: + /* Error occurred on load or store */ + /* Free lock */ + stw %r20, 0(%sr2,%r20) + ssm PSW_SM_I, %r0 + ldo 1(%r0),%r28 + b lws_exit + ldo -EFAULT(%r0),%r21 /* set errno */ + nop + nop + nop + + /* Exception table entries, for the load and store, return EFAULT. + Each of the entries must be relocated. */ + ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(8b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(13b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(17b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(18b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(19b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(20b-linux_gateway_page, 22b-linux_gateway_page) +#ifndef CONFIG_64BIT + ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 22b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(21b-linux_gateway_page, 22b-linux_gateway_page) +#endif + /* Make sure nothing else is placed on this page */ .align PAGE_SIZE END(linux_gateway_page) @@ -675,8 +899,9 @@ ENTRY(end_linux_gateway_page) /* Light-weight-syscall table */ /* Start of lws table. */ ENTRY(lws_table) - LWS_ENTRY(compare_and_swap32) /* 0 - ELF32 Atomic compare and swap */ - LWS_ENTRY(compare_and_swap64) /* 1 - ELF64 Atomic compare and swap */ + LWS_ENTRY(compare_and_swap32) /* 0 - ELF32 Atomic 32bit CAS */ + LWS_ENTRY(compare_and_swap64) /* 1 - ELF64 Atomic 32bit CAS */ + LWS_ENTRY(compare_and_swap_2) /* 2 - ELF32 Atomic 64bit CAS */ END(lws_table) /* End of lws table */ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html