BMC/Intel-BMC/linux.git/arch/s390/lib/spinlock.c, branch dev

s390/spinlock: add compare-and-delay to lock wait loops

2015-01-23T14:17:04+00:00

Add the compare-and-delay instruction to the spin-lock and rw-lock retry loops. A CPU executing the compare-and-delay instruction stops until the lock value has changed. This is done to make the locking code for contended locks to behave better in regard to the multi- hreading facility. A thread of a core executing a compare-and-delay will allow the other threads of a core to get a larger share of the core resources. Signed-off-by: Martin Schwidefsky

s390/rwlock: use the interlocked-access facility 1 instructions

2014-09-25T08:52:13+00:00

Make use of the load-and-add, load-and-or and load-and-and instructions to atomically update the read-write lock without a compare-and-swap loop. Signed-off-by: Martin Schwidefsky

s390/rwlock: improve writer fairness

2014-09-25T08:52:12+00:00

Set the write-lock bit in the out-of-line rwlock code to indicate that a writer is waiting. Additional readers will no be able to get the lock until at least one writer got the lock. Additional writers have to wait for the first writer to release the lock again. Signed-off-by: Martin Schwidefsky

s390/rwlock: remove interrupt-enabling rwlock variant.

2014-09-25T08:52:10+00:00

Signed-off-by: Martin Schwidefsky

s390/rwlock: use directed yield for write-locked rwlocks

2014-09-25T08:52:05+00:00

Add an owner field to the arch_rwlock_t to be able to pass the timeslice of a virtual CPU with diagnose 0x9c to the lock owner in case the rwlock is write-locked. The undirected yield in case the rwlock is acquired writable but the lock is read-locked is removed. Signed-off-by: Martin Schwidefsky

s390/spinlock: refactor arch_spin_lock_wait[_flags]

2014-05-20T06:58:55+00:00

Reorder the spinlock wait code to make it more readable. Signed-off-by: Martin Schwidefsky

s390/rwlock: add missing local_irq_restore calls

2014-05-20T06:58:54+00:00

The out of line _raw_read_lock_wait_flags/_raw_write_lock_wait_flags functions for the arch_read_lock_flags/arch_write_lock_flags calls fail to re-enable the interrupts after another unsuccessful try to get the lock with compare-and-swap. The following wait would be done with interrupts disabled which is suboptimal. Signed-off-by: Martin Schwidefsky

s390/spinlock,rwlock: always to a load-and-test first

2014-05-20T06:58:53+00:00

In case a lock is contended it is better to do a load-and-test first before trying to get the lock with compare-and-swap. This helps to avoid unnecessary cache invalidations of the cacheline for the lock if the CPU has to wait for the lock. For an uncontended lock doing the compare-and-swap directly is a bit better, if the CPU does not have the cacheline in its cache yet the compare-and-swap will get it read-write immediately while a load-and-test would get it read-only first. Always to the load-and-test first to avoid the cacheline invalidations for the contended case outweight the potential read-only to read-write cacheline upgrade for the uncontended case. Signed-off-by: Martin Schwidefsky

s390/spinlock: fix system hang with spin_retry <= 0

2014-05-20T06:58:52+00:00

On LPAR, when spin_retry is set to <= 0, arch_spin_lock_wait() and arch_spin_lock_wait_flags() may end up in a while(1) loop w/o doing any compare and swap operation. To fix this, use do/while instead of for loop. Signed-off-by: Gerald Schaefer Signed-off-by: Martin Schwidefsky

s390/spinlock: optimize spinlock code sequence

2014-05-20T06:58:42+00:00

Use lowcore constant to improve the code generated for spinlocks. [ Martin Schwidefsky: patch breakdown and code beautification ] Signed-off-by: Philipp Hachtmann Signed-off-by: Martin Schwidefsky