[PATCH] sparc32 rwlock fix
read_trylock() is broken on sparc32 (doesn't build and didn't work right, actually). Proposed fix: - make "writer holds lock" distinguishable from "reader tries to grab lock" - have __raw_read_trylock() try to acquire the mutex (in LSB of lock), terminating spin if we see that there's writer holding it. Then do the rest as we do in read_lock(). Thanks to Ingo for discussion... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -87,6 +87,7 @@ extern void ___set_bit(void);
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extern void ___clear_bit(void);
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extern void ___clear_bit(void);
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extern void ___change_bit(void);
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extern void ___change_bit(void);
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extern void ___rw_read_enter(void);
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extern void ___rw_read_enter(void);
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extern void ___rw_read_try(void);
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extern void ___rw_read_exit(void);
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extern void ___rw_read_exit(void);
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extern void ___rw_write_enter(void);
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extern void ___rw_write_enter(void);
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@ -104,8 +105,9 @@ extern unsigned _Urem(unsigned, unsigned);
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EXPORT_SYMBOL(sparc_cpu_model);
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EXPORT_SYMBOL(sparc_cpu_model);
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EXPORT_SYMBOL(kernel_thread);
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EXPORT_SYMBOL(kernel_thread);
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#ifdef CONFIG_SMP
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#ifdef CONFIG_SMP
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// XXX find what uses (or used) these.
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// XXX find what uses (or used) these. AV: see asm/spinlock.h
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EXPORT_SYMBOL(___rw_read_enter);
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EXPORT_SYMBOL(___rw_read_enter);
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EXPORT_SYMBOL(___rw_read_try);
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EXPORT_SYMBOL(___rw_read_exit);
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EXPORT_SYMBOL(___rw_read_exit);
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EXPORT_SYMBOL(___rw_write_enter);
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EXPORT_SYMBOL(___rw_write_enter);
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#endif
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#endif
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@ -25,6 +25,15 @@ ___rw_read_enter_spin_on_wlock:
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ldstub [%g1 + 3], %g2
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ldstub [%g1 + 3], %g2
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b ___rw_read_enter_spin_on_wlock
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b ___rw_read_enter_spin_on_wlock
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ldub [%g1 + 3], %g2
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ldub [%g1 + 3], %g2
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___rw_read_try_spin_on_wlock:
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andcc %g2, 0xff, %g0
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be,a ___rw_read_try
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ldstub [%g1 + 3], %g2
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xnorcc %g2, 0x0, %o0 /* if g2 is ~0, set o0 to 0 and bugger off */
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bne,a ___rw_read_enter_spin_on_wlock
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ld [%g1], %g2
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retl
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mov %g4, %o7
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___rw_read_exit_spin_on_wlock:
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___rw_read_exit_spin_on_wlock:
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orcc %g2, 0x0, %g0
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orcc %g2, 0x0, %g0
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be,a ___rw_read_exit
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be,a ___rw_read_exit
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@ -60,6 +69,17 @@ ___rw_read_exit:
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retl
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retl
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mov %g4, %o7
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mov %g4, %o7
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.globl ___rw_read_try
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___rw_read_try:
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orcc %g2, 0x0, %g0
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bne ___rw_read_try_spin_on_wlock
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ld [%g1], %g2
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add %g2, 1, %g2
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st %g2, [%g1]
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set 1, %o1
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retl
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mov %g4, %o7
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.globl ___rw_write_enter
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.globl ___rw_write_enter
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___rw_write_enter:
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___rw_write_enter:
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orcc %g2, 0x0, %g0
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orcc %g2, 0x0, %g0
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@ -129,6 +129,7 @@ static inline void __raw_write_lock(raw_rwlock_t *rw)
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: /* no outputs */
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: /* no outputs */
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: "r" (lp)
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: "r" (lp)
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: "g2", "g4", "memory", "cc");
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: "g2", "g4", "memory", "cc");
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*(volatile __u32 *)&lp->lock = ~0U;
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}
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}
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static inline int __raw_write_trylock(raw_rwlock_t *rw)
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static inline int __raw_write_trylock(raw_rwlock_t *rw)
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@ -144,15 +145,40 @@ static inline int __raw_write_trylock(raw_rwlock_t *rw)
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val = rw->lock & ~0xff;
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val = rw->lock & ~0xff;
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if (val)
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if (val)
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((volatile u8*)&rw->lock)[3] = 0;
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((volatile u8*)&rw->lock)[3] = 0;
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else
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*(volatile u32*)&rw->lock = ~0U;
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}
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}
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return (val == 0);
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return (val == 0);
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}
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}
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static inline int __read_trylock(raw_rwlock_t *rw)
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{
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register raw_rwlock_t *lp asm("g1");
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register int res asm("o0");
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lp = rw;
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__asm__ __volatile__(
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"mov %%o7, %%g4\n\t"
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"call ___rw_read_try\n\t"
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" ldstub [%%g1 + 3], %%g2\n"
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: "=r" (res)
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: "r" (lp)
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: "g2", "g4", "memory", "cc");
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return res;
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}
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#define __raw_read_trylock(lock) \
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({ unsigned long flags; \
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int res; \
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local_irq_save(flags); \
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res = __read_trylock(lock); \
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local_irq_restore(flags); \
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res; \
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})
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#define __raw_write_unlock(rw) do { (rw)->lock = 0; } while(0)
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#define __raw_write_unlock(rw) do { (rw)->lock = 0; } while(0)
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#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
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#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
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#define __raw_read_trylock(lock) generic__raw_read_trylock(lock)
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#define _raw_spin_relax(lock) cpu_relax()
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#define _raw_spin_relax(lock) cpu_relax()
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#define _raw_read_relax(lock) cpu_relax()
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#define _raw_read_relax(lock) cpu_relax()
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