src/sys/compat/linux/linux_futex.c, branch releng/7.3

MFC r194203:

2009-06-17T16:56:21Z

Unlock process lock when return error from getrobustlist call. Approved by: kib (mentor)

MFC r191887:

2009-06-06T10:59:36Z

Add KTR(9) tracing for futex emulation. Approved by: kib (mentor)

MFC r191741:

2009-06-01T04:44:43Z

Move extern variable definitions to the header file. Approved by: kib (mentor)

MFC r191719:

2009-05-31T06:58:35Z

Reimplement futexes. Old implemention used Giant to protect the kernel data structures, but at the same time called malloc(M_WAITOK), that could cause the calling thread to sleep and lost Giant protection. User-visible result was the missed wakeup. New implementation uses one sx lock per futex. The sx protects the futex structures and allows to sleep while copyin or copyout are performed. Unlike linux, we return EINVAL when FUTEX_CMP_REQUEUE operation is requested and either caller specified futexes are equial or second futex already exists. This is acceptable since the situation can only occur from the application error, and glibc falls back to old FUTEX_WAKE operation when FUTEX_CMP_REQUEUE returns an error. Approved by: kib (mentor)

Merge r191269 from HEAD to stable/7:

2009-05-25T14:36:21Z

Remove support for FUTEX_REQUEUE operation. Glibc does not use this operation since 2.3.3 version (Jun 2004), as it is racy and replaced by FUTEX_CMP_REQUEUE operation. Glibc versions prior to 2.3.3 fall back to FUTEX_WAKE when FUTEX_REQUEUE returned EINVAL. Any application directly using FUTEX_REQUEUE without return value checking are definitely broken. Limit quantity of messages per process about unsupported operation. Approved by: kib(mentor)

Merge from HEAD to stable/7:

2009-05-05T15:19:45Z

r189861: Include linux_futex.h before linux_emul.h r189862: Ignore FUTEX_FD op, as it is done by linux. r189867: Sort include files in the alphabetical order. Approved by: kib (mentor)

Merge from HEAD to stable/7:

2009-05-05T14:53:58Z

r178976 (rdivacky): Implement robust futexes. Most of the code is modelled after what Linux does. This is because robust futexes are mostly userspace thing which we cannot alter. Two syscalls maintain pointer to userspace list and when process exits a routine walks this list waking up processes sleeping on futexes from that list. r183871: Make robust futexes work on linux32/amd64. Use PTRIN to read user-mode pointers. Change types used in the structures definitions to properly-sized architecture-specific types. r185002: In the robust futexes list head, futex_offset shall be signed, and glibc actually supplies negative offsets. Change l_ulong to l_long. Approved by: kib (mentor)

MFC rev. 1.12 of sys/compat/linux/linux_futex.c

2008-03-28T10:13:20Z

MFC rev. 1.3 of sys/compat/linux/linux_futex.h: o Add stub support for some new futex operations, so the annoying message is not printed. o Don't warn about FUTEX_FD not being implemented and return ENOSYS instead of 0 (eg. success). o Clear FUTEX_PRIVATE_FLAG as we actually implement only private futexes so there is no reason to return ENOSYS when app asks for a private futex. We don't reject shared futexes because they worked just fine with our implementation so far. Approved by: kib (mentor) Tested by: bsam

MFC rev. 1.11:

2008-03-09T13:59:19Z

Return ENOSYS instead of 0 for the unknown futex operations.

Move futex support code from /support.s into linux compat directory.

2007-05-23T08:33:06Z

Implement all futex atomic operations in assembler to not depend on the fuword() that does not allow to distinguish between -1 and failure return. Correctly return 0 from atomic operations on success. In collaboration with: rdivacky Tested by: Scot Hetzel , Milos Vyletel Sponsored by: Google SoC 2007