Date: Mon, 11 Sep 2000 13:37:29 -0700 (PDT) From: John Baldwin <jhb@pike.osd.bsdi.com> To: dfr@FreeBSD.org Cc: alpha@FreeBSD.org Subject: Bug in spinlocks? Message-ID: <200009112037.NAA61735@pike.osd.bsdi.com>
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Hmm, is there any reason why we aren't disabling interrupts on the alpha
when we obtain spinlocks? In the i386 code we use the following macro:
/* Get a spin lock, handle recursion inline (as the less common case) */
#define _getlock_spin_block(mp, tid, type) do { \
u_int _mtx_fl = read_eflags(); \
disable_intr(); \
if (atomic_cmpset_int(&(mp)->mtx_lock, MTX_UNOWNED, (tid)) == 0) \
mtx_enter_hard(mp, (type) & MTX_HARDOPTS, _mtx_fl); \
else \
(mp)->mtx_savefl = _mtx_fl; \
} while (0)
on the alpha it is almost the same:
/*
* Get a spin lock, handle recusion inline (as the less common case)
*/
#define _getlock_spin_block(mp, tid, type) do { \
u_int _ipl = alpha_pal_rdps() & ALPHA_PSL_IPL_MASK; \
if (atomic_cmpset_64(&(mp)->mtx_lock, MTX_UNOWNED, (tid)) == 0) \
mtx_enter_hard(mp, (type) & MTX_HARDOPTS, _ipl); \
else { \
alpha_mb(); \
(mp)->mtx_saveipl = _ipl; \
} \
} while (0)
Note that in the alpha we are just saving and restoring the ipl, but we
aren't actually changing it to disable interrupts.
--
John Baldwin <jhb@bsdi.com> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.cslab.vt.edu/~jobaldwi/pgpkey.asc
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