linux/Documentation/powerpc
Sam bobroff b4b56f9eca powerpc/tm: Abort syscalls in active transactions
This patch changes the syscall handler to doom (tabort) active
transactions when a syscall is made and return very early without
performing the syscall and keeping side effects to a minimum (no CPU
accounting or system call tracing is performed). Also included is a
new HWCAP2 bit, PPC_FEATURE2_HTM_NOSC, to indicate this
behaviour to userspace.

Currently, the system call instruction automatically suspends an
active transaction which causes side effects to persist when an active
transaction fails.

This does change the kernel's behaviour, but in a way that was
documented as unsupported.  It doesn't reduce functionality as
syscalls will still be performed after tsuspend; it just requires that
the transaction be explicitly suspended.  It also provides a
consistent interface and makes the behaviour of user code
substantially the same across powerpc and platforms that do not
support suspended transactions (e.g. x86 and s390).

Performance measurements using
http://ozlabs.org/~anton/junkcode/null_syscall.c indicate the cost of
a normal (non-aborted) system call increases by about 0.25%.

Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2015-06-19 17:10:28 +10:00
..
00-INDEX powerpc/dscr: Add documentation for DSCR support 2015-06-07 19:29:27 +10:00
bootwrapper.txt
cpu_families.txt powerpc: Add cpu family documentation 2014-06-05 13:20:01 +10:00
cpu_features.txt
cxl.txt cxl: Document external user of existing API 2015-06-03 13:27:16 +10:00
dscr.txt powerpc/dscr: Add documentation for DSCR support 2015-06-07 19:29:27 +10:00
eeh-pci-error-recovery.txt
firmware-assisted-dump.txt
hvcs.txt
mpc52xx.txt
pci_iov_resource_on_powernv.txt powerpc/pci: Add PCI resource alignment documentation 2015-03-31 13:02:38 +11:00
pmu-ebb.txt
ptrace.txt
qe_firmware.txt
transactional_memory.txt powerpc/tm: Abort syscalls in active transactions 2015-06-19 17:10:28 +10:00