I see you've made some R/W semaphore changes...
| /*
| * nested locking:
| */
This comment is inadequate. Please be more explicit about when you're allowed
to do this.
| extern void down_read_nested(struct rw_semaphore *sem, int subclass);
| extern void down_write_nested(struct rw_semaphore *sem, int subclass);
Please, please, please don't. R/W semaphores are _not_ permitted to nest.
That way lies deadlock.
| /*
| * Take/release a lock when not the owner will release it:
| */
| extern void down_read_non_owner(struct rw_semaphore *sem);
| extern void up_read_non_owner(struct rw_semaphore *sem);
Does that mean that the owner may not then release the semaphore? I presume
not, but it's not entirely clear.
| # define down_read_nested(sem, subclass) down_read(sem)
| # define down_write_nested(sem, subclass) down_write(sem)
This is _not_ okay.
I also notice that you've out-of-lined the rwsems debugging wrappers in all
situations. Please don't. On some archs this is going to slow things down.
On FRV for example, this is converted to:
0xc00437f0 <down_read+0>: addi sp,-16,sp
0xc00437f4 <down_read+4>: sti fp,@(sp,0)
0xc00437f8 <down_read+8>: ori sp,0,fp
0xc00437fc <down_read+12>: movsg lr,gr5
0xc0043800 <down_read+16>: sti gr5,@(fp,8)
0xc0043804 <down_read+20>: call 0xc01ea910 <__down_read>
0xc0043808 <down_read+24>: ldi @(fp,8),gr5
0xc004380c <down_read+28>: ld @(fp,gr0),fp
0xc0043810 <down_read+32>: addi sp,16,sp
0xc0043814 <down_read+36>: jmpl @(gr5,gr0)
When previously __down_read would be called directly... This applies to every
arch that uses the spinlock-based R/W sems. In FRV's case, you've required
the loading of extra icache lines to no useful purpose. Now I do have GDB
stub compiled in, so normally it would be shorter than this as it wouldn't
normally save the frame pointer, and would probably tail-call.
If you must put your annotations somewhere, please place them in lib/rwsem*.c
directly.
Please _only_ out-of-line the rwsem debugging wrappers when the appropriate
config options are set. It is reasonable to do it then - it is debugging code
after all, and therefore not enabled for normal operation.
Oh, and if you're going to out-of-line the rwsem debugging wrappers like this,
please remove all the then-redundant PUSHL instructions from the inline asm in
include/asm-i386/rwsem.h. They're then no longer required as there's no need
to save registers that are callee-clobbered, since you're marking them
clobbered anyway by interpolating an extra function call.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
