mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-23 17:22:01 +07:00
916633a403
Now that all the architectures implement the necessary glue code we can introduce down_write_killable(). The only difference wrt. regular down_write() is that the slow path waits in TASK_KILLABLE state and the interruption by the fatal signal is reported as -EINTR to the caller. Signed-off-by: Michal Hocko <mhocko@suse.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Zankel <chris@zankel.net> Cc: David S. Miller <davem@davemloft.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Max Filippov <jcmvbkbc@gmail.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Cc: Signed-off-by: Jason Low <jason.low2@hp.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> Cc: linux-alpha@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: linux-ia64@vger.kernel.org Cc: linux-s390@vger.kernel.org Cc: linux-sh@vger.kernel.org Cc: linux-xtensa@linux-xtensa.org Cc: sparclinux@vger.kernel.org Link: http://lkml.kernel.org/r/1460041951-22347-12-git-send-email-mhocko@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
236 lines
6.7 KiB
C
236 lines
6.7 KiB
C
/* rwsem.h: R/W semaphores implemented using XADD/CMPXCHG for i486+
|
|
*
|
|
* Written by David Howells (dhowells@redhat.com).
|
|
*
|
|
* Derived from asm-x86/semaphore.h
|
|
*
|
|
*
|
|
* The MSW of the count is the negated number of active writers and waiting
|
|
* lockers, and the LSW is the total number of active locks
|
|
*
|
|
* The lock count is initialized to 0 (no active and no waiting lockers).
|
|
*
|
|
* When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an
|
|
* uncontended lock. This can be determined because XADD returns the old value.
|
|
* Readers increment by 1 and see a positive value when uncontended, negative
|
|
* if there are writers (and maybe) readers waiting (in which case it goes to
|
|
* sleep).
|
|
*
|
|
* The value of WAITING_BIAS supports up to 32766 waiting processes. This can
|
|
* be extended to 65534 by manually checking the whole MSW rather than relying
|
|
* on the S flag.
|
|
*
|
|
* The value of ACTIVE_BIAS supports up to 65535 active processes.
|
|
*
|
|
* This should be totally fair - if anything is waiting, a process that wants a
|
|
* lock will go to the back of the queue. When the currently active lock is
|
|
* released, if there's a writer at the front of the queue, then that and only
|
|
* that will be woken up; if there's a bunch of consecutive readers at the
|
|
* front, then they'll all be woken up, but no other readers will be.
|
|
*/
|
|
|
|
#ifndef _ASM_X86_RWSEM_H
|
|
#define _ASM_X86_RWSEM_H
|
|
|
|
#ifndef _LINUX_RWSEM_H
|
|
#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
|
|
#endif
|
|
|
|
#ifdef __KERNEL__
|
|
#include <asm/asm.h>
|
|
|
|
/*
|
|
* The bias values and the counter type limits the number of
|
|
* potential readers/writers to 32767 for 32 bits and 2147483647
|
|
* for 64 bits.
|
|
*/
|
|
|
|
#ifdef CONFIG_X86_64
|
|
# define RWSEM_ACTIVE_MASK 0xffffffffL
|
|
#else
|
|
# define RWSEM_ACTIVE_MASK 0x0000ffffL
|
|
#endif
|
|
|
|
#define RWSEM_UNLOCKED_VALUE 0x00000000L
|
|
#define RWSEM_ACTIVE_BIAS 0x00000001L
|
|
#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
|
|
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
|
|
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
|
|
|
|
/*
|
|
* lock for reading
|
|
*/
|
|
static inline void __down_read(struct rw_semaphore *sem)
|
|
{
|
|
asm volatile("# beginning down_read\n\t"
|
|
LOCK_PREFIX _ASM_INC "(%1)\n\t"
|
|
/* adds 0x00000001 */
|
|
" jns 1f\n"
|
|
" call call_rwsem_down_read_failed\n"
|
|
"1:\n\t"
|
|
"# ending down_read\n\t"
|
|
: "+m" (sem->count)
|
|
: "a" (sem)
|
|
: "memory", "cc");
|
|
}
|
|
|
|
/*
|
|
* trylock for reading -- returns 1 if successful, 0 if contention
|
|
*/
|
|
static inline int __down_read_trylock(struct rw_semaphore *sem)
|
|
{
|
|
long result, tmp;
|
|
asm volatile("# beginning __down_read_trylock\n\t"
|
|
" mov %0,%1\n\t"
|
|
"1:\n\t"
|
|
" mov %1,%2\n\t"
|
|
" add %3,%2\n\t"
|
|
" jle 2f\n\t"
|
|
LOCK_PREFIX " cmpxchg %2,%0\n\t"
|
|
" jnz 1b\n\t"
|
|
"2:\n\t"
|
|
"# ending __down_read_trylock\n\t"
|
|
: "+m" (sem->count), "=&a" (result), "=&r" (tmp)
|
|
: "i" (RWSEM_ACTIVE_READ_BIAS)
|
|
: "memory", "cc");
|
|
return result >= 0 ? 1 : 0;
|
|
}
|
|
|
|
/*
|
|
* lock for writing
|
|
*/
|
|
#define ____down_write(sem, slow_path) \
|
|
({ \
|
|
long tmp; \
|
|
struct rw_semaphore* ret; \
|
|
asm volatile("# beginning down_write\n\t" \
|
|
LOCK_PREFIX " xadd %1,(%3)\n\t" \
|
|
/* adds 0xffff0001, returns the old value */ \
|
|
" test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t" \
|
|
/* was the active mask 0 before? */\
|
|
" jz 1f\n" \
|
|
" call " slow_path "\n" \
|
|
"1:\n" \
|
|
"# ending down_write" \
|
|
: "+m" (sem->count), "=d" (tmp), "=a" (ret) \
|
|
: "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS) \
|
|
: "memory", "cc"); \
|
|
ret; \
|
|
})
|
|
|
|
static inline void __down_write(struct rw_semaphore *sem)
|
|
{
|
|
____down_write(sem, "call_rwsem_down_write_failed");
|
|
}
|
|
|
|
static inline int __down_write_killable(struct rw_semaphore *sem)
|
|
{
|
|
if (IS_ERR(____down_write(sem, "call_rwsem_down_write_failed_killable")))
|
|
return -EINTR;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* trylock for writing -- returns 1 if successful, 0 if contention
|
|
*/
|
|
static inline int __down_write_trylock(struct rw_semaphore *sem)
|
|
{
|
|
long result, tmp;
|
|
asm volatile("# beginning __down_write_trylock\n\t"
|
|
" mov %0,%1\n\t"
|
|
"1:\n\t"
|
|
" test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t"
|
|
/* was the active mask 0 before? */
|
|
" jnz 2f\n\t"
|
|
" mov %1,%2\n\t"
|
|
" add %3,%2\n\t"
|
|
LOCK_PREFIX " cmpxchg %2,%0\n\t"
|
|
" jnz 1b\n\t"
|
|
"2:\n\t"
|
|
" sete %b1\n\t"
|
|
" movzbl %b1, %k1\n\t"
|
|
"# ending __down_write_trylock\n\t"
|
|
: "+m" (sem->count), "=&a" (result), "=&r" (tmp)
|
|
: "er" (RWSEM_ACTIVE_WRITE_BIAS)
|
|
: "memory", "cc");
|
|
return result;
|
|
}
|
|
|
|
/*
|
|
* unlock after reading
|
|
*/
|
|
static inline void __up_read(struct rw_semaphore *sem)
|
|
{
|
|
long tmp;
|
|
asm volatile("# beginning __up_read\n\t"
|
|
LOCK_PREFIX " xadd %1,(%2)\n\t"
|
|
/* subtracts 1, returns the old value */
|
|
" jns 1f\n\t"
|
|
" call call_rwsem_wake\n" /* expects old value in %edx */
|
|
"1:\n"
|
|
"# ending __up_read\n"
|
|
: "+m" (sem->count), "=d" (tmp)
|
|
: "a" (sem), "1" (-RWSEM_ACTIVE_READ_BIAS)
|
|
: "memory", "cc");
|
|
}
|
|
|
|
/*
|
|
* unlock after writing
|
|
*/
|
|
static inline void __up_write(struct rw_semaphore *sem)
|
|
{
|
|
long tmp;
|
|
asm volatile("# beginning __up_write\n\t"
|
|
LOCK_PREFIX " xadd %1,(%2)\n\t"
|
|
/* subtracts 0xffff0001, returns the old value */
|
|
" jns 1f\n\t"
|
|
" call call_rwsem_wake\n" /* expects old value in %edx */
|
|
"1:\n\t"
|
|
"# ending __up_write\n"
|
|
: "+m" (sem->count), "=d" (tmp)
|
|
: "a" (sem), "1" (-RWSEM_ACTIVE_WRITE_BIAS)
|
|
: "memory", "cc");
|
|
}
|
|
|
|
/*
|
|
* downgrade write lock to read lock
|
|
*/
|
|
static inline void __downgrade_write(struct rw_semaphore *sem)
|
|
{
|
|
asm volatile("# beginning __downgrade_write\n\t"
|
|
LOCK_PREFIX _ASM_ADD "%2,(%1)\n\t"
|
|
/*
|
|
* transitions 0xZZZZ0001 -> 0xYYYY0001 (i386)
|
|
* 0xZZZZZZZZ00000001 -> 0xYYYYYYYY00000001 (x86_64)
|
|
*/
|
|
" jns 1f\n\t"
|
|
" call call_rwsem_downgrade_wake\n"
|
|
"1:\n\t"
|
|
"# ending __downgrade_write\n"
|
|
: "+m" (sem->count)
|
|
: "a" (sem), "er" (-RWSEM_WAITING_BIAS)
|
|
: "memory", "cc");
|
|
}
|
|
|
|
/*
|
|
* implement atomic add functionality
|
|
*/
|
|
static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
|
|
{
|
|
asm volatile(LOCK_PREFIX _ASM_ADD "%1,%0"
|
|
: "+m" (sem->count)
|
|
: "er" (delta));
|
|
}
|
|
|
|
/*
|
|
* implement exchange and add functionality
|
|
*/
|
|
static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
|
|
{
|
|
return delta + xadd(&sem->count, delta);
|
|
}
|
|
|
|
#endif /* __KERNEL__ */
|
|
#endif /* _ASM_X86_RWSEM_H */
|