9 Nov
2017
9 Nov
'17
7:09 p.m.
On 11/09/2017 05:18 AM, Cupertino Miranda wrote:
Hi Waldemar,
I personally made this tst-cancel test start to pass in the past,
related to unwinding issues we had in our tools.
However, I have noticed that some of the tst-cancel tests would have
some non-deterministic behavior.
This was related to some pipes not blocking, when writing some data, but
not blocking.
If I increased the written elements to the pipe, those would block
always, and the test would pass.
It is possible that there was some change in the kernel that might have
fixed this.
Vineet: Do you know anything about this ?
Not in ARC port per se.
Regarding your patch I would advise not to apply it
until we find the
real reason for blink not to be restored.
Right. Although in SNPS github uclibc repo we carry an equivalent patch (from
Cuper) for fixing some of the cancelation tests. That is the only out of tree
patch we have in uClibc just because we (I) didn't have time to analyze things
fully. However I'm planning to clean this up and prove that we need that patch
(and submit it for merge) or prove it is useless - which is quite unlikely - since
Cuper is generally NOT smoking pot when coding ;-)
OTOH, while we do need this analysis, the change itself seemed relatively benign,
but was kept on hold due to reasons needing a historic detour (read below if
interested)
In 2010 ? I rewrote the uClibc syscall generators. To reduce generated code bloat
and stack spills for prologue/epilogue etc ernro handling was moved into an
out-of-line function. For fast path case of a simpler successful syscalls (no
errno), no stack operations were needed.
0000c244 <__libc_nanosleep>:
c244: mov r8,162
c248: swi
c24c: brge r0,0,c25c
c250: st.a blink, [sp,-4] # this blink save is from inline
asm - not gcc
c254: bl ad5c # this is errno setter
c258: ld.ab blink, [sp,4]
c25c: j_s [blink]
c25e: nop_s
The proposed change adds blink to clobber list, making BLINK saved twice now (once
by gcc and other due to above) and also undoes all the hand crafted beauty above.
-Vineet