Hello,
Could someone please explain why mtx_trylock() must not be called on a spin
mutex?
Is it conceptually wrong or is it a restriction of FreeBSD kernel
implementation?
I've written slightly modified version of mtx_trylock (mtx_trylock_spin) which
calls
spinlock_enter/spinlock_exit and doesn't have KASSERT checking for lock class:
KASSERT(m->mtx_object.lo_class == &lock_class_mtx_sleep,
("mtx_trylock() of spin mutex %s @ %s:%d",
m->mtx_object.lo_name,
file, line));
but, to my surprise, all my tests passed w/o any errors/warnings on FreeBSD-8
with WITNESS/INVARIANTS/etc enabled.
I admit that my tests may not cover all possible use cases or scenarios though.
I did a quick google search but didn't find anything useful, so your help is
greatly appreciated.
Thanks in advance!
P.S.
The assertion was added in the following revision:
Revision 149737 - (view) (annotate) - [select for diffs]
Modified Fri Sep 2 20:21:49 2005 UTC (6 years, 4 months ago) by jhb
File length: 24623 byte(s)
Diff to previous 148557
- Add an assertion to panic if one tries to call mtx_trylock() on a spin
mutex.
- Don't panic if a spin lock is held too long inside _mtx_lock_spin() if
panicstr is set (meaning that we are already in a panic). Just keep
spinning forever instead.
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