From dc097e32d8094c54ed2cd71a2ed6b7739b5897ca Mon Sep 17 00:00:00 2001
From: Sean Cross <sean@xobs.io>
Date: Thu, 2 Feb 2023 23:06:32 +0800
Subject: [PATCH] kernel: fix atomic operations

Atomic operations were previously broken. RISC-V breaks atomic
operations into multiple instructions, and there is some state kept
between those instructions. This state is not visible, and is internal
to the processor.

We were ignoring this state, which resulted in inconsistencies
throughout the system. The following sequence was possible:

1. A thread loads a value, and obtains the `reservation set`
2. A context switch happens on the following instruction
3. A different thread loads the value, modifies it, and continues
4. A third thread (or a different process) loads a value and obtains the
   `reservation set`
5. The original thread runs, sees the `reservation set` is held, and
   updates the value, clobbering what the second thread did in #3

A workaround for this is to perform a dummy `sc` as part of the context
switch. This invalidates any atomic operations that may be pending.

Signed-off-by: Sean Cross <sean@xobs.io>
---
 kernel/bin/riscv32i-unknown-none-elf.a    | Bin 9062 -> 10102 bytes
 kernel/bin/riscv32imac-unknown-none-elf.a | Bin 8870 -> 9982 bytes
 kernel/bin/riscv32imac-unknown-xous-elf.a | Bin 8870 -> 9982 bytes
 kernel/bin/riscv32imc-unknown-none-elf.a  | Bin 8870 -> 9982 bytes
 kernel/bin/riscv64gc-unknown-none-elf.a   | Bin 14238 -> 16086 bytes
 kernel/bin/riscv64imac-unknown-none-elf.a | Bin 14238 -> 16086 bytes
 kernel/src/asm.S                          |  20 ++++++++++++++++++++
 7 files changed, 20 insertions(+)

diff --git a/kernel/bin/riscv32i-unknown-none-elf.a b/kernel/bin/riscv32i-unknown-none-elf.a
index bc88a1f90b914febb384ac02b03e013226dc04e9..7342c6ca3d20a3401a64e9e6a3ba792455e67f94 100644
GIT binary patch
delta 1968
zcmbtUOG{Nz6h7ONx8ozd4>Nm^$8&360|!?$A0VL(vPmjbPy`i}5EPLR)WEtyh1yGP
zTV_^T*~1=?U5iFd8U+1;Xb{w-K{RL-1r1u?UVD3Qr(qk;KHvAPZ?ARs+IQbCn|^eS
ztnixGH>^)LG`EZf*J~{H{j`t4bA3A9)YRnrtu4)?AJ-**296$$daiYrIhEPvqNt!F
zLBjt$)7hjuDa2y+*_~9M+_*YaxJJa(XyLnJr?3Fk+=&A9-QA_OM>dE$H6BT+XAw`m
zj`ZN2EnD30sjuZ_8P5^=+w8=Ak);lEFT_hjJR0H^Azl^Yt1Qo$0=^XtUlZcBAzl~a
z=@93JL*xy#gyL<6yJS#9<!jaMqGI8xU*+93yr4aA!2%@UIwf#*{OkI=k5S#%;)SKm
zlR2(tqt%I`1rFdkF-NF+f2r#6yqdC5EZ1Z9CbA!*fmr@LXKOGJr&sk<Rm79^S(ebQ
z*gRvjD)xdg+7x@q7~$BwIuKtSX`{A?f$XVxLWuF~SmJGQ=9*bR5qXwzC*fc)hvfj{
zEzpN@SQ^h(=;v4mmd3La`gzuYrSa^6eu4E2h%}~N1TJy_SQ^to=$BXrmd4WueVBD%
zX*|cEkFX9bjpqdPQPzRwh?CLmGy<1704$AZ2)be&SQ^hT^fA_frSV*WeuZ^lX*`qA
zud)s-jc3ZG`oRPTrVucu2ub1*>!rYt8RNGio-nQee!v*_P&{OeJ1Axu>patp_1fEv
zu{L>!ChQ+1Wdb_UT@q*@QF2B@jZ;SVNfP&1$9+!T&*7BOJ$SCOt~W5rSbxL~#;ChO
z++?B)-(swHFr^x+yB75x-oGz<vbskU)g~P05XCFhd%rU?Mhtn81DnLv0Pmy+7Zw^u
z8~tatYs8bi%-e`sj7UHEX6OLyu(56ukh|Rkrm60QCDb+)#x1vndkNb`@cQ%x0e~4c
zwwHK*!nzvA*-RSpm6#Yd(npV7L(ths`QiY2P$O*c3<(w^wu6jmZQ=<hfq|3GFMN~=
zA14ik@t0&bf}b+-*&KrrwKu4Y<LvXxyo#u3P}zzT%g_3avfAy$ObpwZqlemigkE}l
mQtyM*lHc^L)3ocQq|K?4<jR5@aaEg?RgKiTH^z#Wt^5bL-lT~D

delta 1099
zcmZ9KJ#5oZ5XbN3yHP`JC#_Nnts7f$s4_VH2&q(w4i#mn%7;22BnH$8gisj}OGH3|
zQYaq@2UH?ZSV0URGaxar!OF<O3Ns5ccRs&1?Mct?ckkZ)?|k;Z<=@BK2Q!nilSgN2
z4Zl-*F|OIReVa|5HQ%q->$cr!Om%)8$s1!3+I0A=zz_@u!>TW)W`fmtSE(3|C%R}S
zEPS7I@jzk%Z>0LMns9L<brn<TMuHMuJeKzGO8QjrE#1uE8Pmmeb8bMC<r#-8-ZD>~
z9sorL*`1L1PLIEX1aau^b;-}{^9}rHjbYm|%su7krWO3PN^1D!Zo*WA+;VXXs|Ba_
zN{*_uncKoX^J`(Aiup$P6Z1CSEQ|*43OS|LgU^HCv#q-losI*P?+B-8Q%{AtfAvh*
zV16!KVD1PPnV$$BVn*Rm=YepT`%sv3okzmw*zux3DD+qYEabFz*^AD3fNDd|!{+V@
zhXw8nhs|wb!C4M2IZLX~Faa)8D34#=#a5F%&dk%|7I~cPFVW(Ut8Fd@FiT_6relkA
zz&Z0#V1x8nfc3aLt#_VS=MciRBtQwE#T=Rro+WRO;9-ChbjE`Gr)j~9#5#u%wn)%o
zh)l<t<ZI^82f9~@?f@)Em+W7s)m!)n6<(n;E}V;EJef^eEa=l>`<cYG^3a7YVQ-xb
zP1ELhWIPNu{$+a0xT7M)W%#q{_j^lB^IoGZv<m(yd$|Qtou@JINA2Q>Hxj#TV8bgH
NS4iedbd@*V%744}U~vEd

diff --git a/kernel/bin/riscv32imac-unknown-none-elf.a b/kernel/bin/riscv32imac-unknown-none-elf.a
index c2cb641f57415acc6d5c951146a4308358e55f5e..8e65db07f4a9479c2e3df404d6a87d04a3e9927e 100644
GIT binary patch
delta 2247
zcmaJ?U1(fI7@gUBce71*H+z$q>{iL%-IYm&LN=yJsx1;9#1hd4>`U;$f(?i*)<Q)o
zlnwYtY_*MJ|B~7mf7)u=G_q|K30kb+iw{A>N9k)p#0MYxP=eo?Z)Wduh0bz!&N<(i
z@7tNVGkf8w^=D6PN{<c?4cCT7x6M}ODh`KXEkxt*!CGx(WF!n98y$Xh_Rq~-(-k44
z5MnDmLTnbjqDL3yl0Ogz1^u%eXOK&bmnHe`_qp7dOw7wRZv!Rtd>wd;dd$n{HF}o)
zLR+?}KcfHf7u!WLfr{SQgbuwI^wH$@gxI2gN%rg8$+Z4EIf1_ML~4)USZ-gFaz!7=
zl=S&bKKKsfOiP)c{=NP&GoaTqWAax$kS&$hTv%}Yw;2DUQO^!Yxvm#-rNIOyZyKBZ
z7*EG|MwdE@^|UGMMhd~)Ovs4L{icC=D#p_>-X7zb7|%Igw*~V~u)H(IyJNg3#tSjN
zDaId)@jlCk+>Ez14Zc~CTx_+%W<0I$<c4KVALuBSc{N&MO&5SCHb&kj|L<*<Fr)IO
zZnSdDtIdpgeW#<;OYdGw^F+Y=r|WISa&uLU!xPb>LhwYFF6LhkZrJg8da0%fr}aYq
zT=AM!siQS94VzxLs&@y~!RxGSq0Wu30e{Onj+}d$UojqiDd<b>^ymQ1G;Ri6Ql4%6
z-uY8|eT1aSyF3b5y~B71^!FmHtY-}R9P7Z!dY*^=KI_10hVdlyqY+lt^CI+PqHZD}
z%9^GS_<#oht7DA!LH{tq%6bk$Kh8R^vYt1fpI{wWS<eyZv#cNSsJ^nMw-ES<1Hj6f
zW}s`<ftB?fhyF3^z{+|~LO;nmu(F<c=%-i*R`6i{iwK<N0I;&Ai_p)o4y>$a3Hm(i
zz{+}X2gu8;<9y32jPcgVWyamWUoplJt;?^O;5^DD#wO8cjLqQB8DntuiwO5y9f{<Z
ztRqkLLWKLR9+D(4vi>l2)k_BN5+MCHfLlwRGXY^{@Cjq{BhE86Ggx433V+JjOkhzT
z>U++gdUfwhjUW0Z<c4Xww)RuJTla=lx+1oR)%stgAvqFZrZ`pLPt$`702<n1BB4S2
z<t~TaL>)$Cj>rmagKI9fiv;8zvw^!*cQs2pj>5P#T;VCgZV<fVN!nik+gxl9@z#Xb
zLLqjNhI|`s3==s>j~hc!?5BKG+qQjC@NJS>jnibTIUn`zPXsS%YvFsL5O0!(!noqx
zL~sC*&*fOr3+3KUyd<qvZYT9bx#w|gXKT_!<!Cm6jbS$5&_k>H8g-_nQ@T)5*{!rq
eH)+-nkl4`AR31$H8|arSs<29VZdornSNcDqWyWp*

delta 1273
zcmZ9K&ubG=5XawZk|jyI?rzeCM6_L#bW=(pn>LB5Am$>~Qfm$#deM3i#2-iz#fy*%
z^=H*KPFumo>PeK|Tu<7A6c4$mARa1+di2zTe}Fpk-fkK)Fgu@lGw=I;?E8D{#o@)>
z!Qs*2{e@h~t|gx&JvL3-B$MBqZ5NA0(<~M9cJ0SNw9?BMXN=|185>|R)&mK?4h=pI
zv5s+GaBg(0av1Wxh4212#zA-)=mI;i47O6>X*jE7U`44o+sbJ_zv3L~{K<{iLX19&
z5Pt(%wGU3II^Te4HOn`lsvh6>sjcfvTmBXPseOFQ(RO7yOlmq@Lf;OB4ZjdoXxqXR
z_@)=Q0t;G#hl#5#HPP#JGNy?<+#Ha3swHnCf{%5zrkDrYa=lI8PjxsL?1bNjZfI@Y
z5jYyT+PoeeuV+^De~#1>^_|`k7fCGs80Mm>+*3I;guz&oY!g3|Oux@~F8Mt18f-;-
zosMpm^IMMIvl*`DeT*e<%NAnmrep;JUy@9x<;#+F;uXo=#5Kur;zyGA5QAi)b6>KU
z`#>_yO+94OBBLbZ7KG4(Y$Bo5;tprrak_4PM~;il-IXjBxF=a`ZXW8%N#{>;f`=+t
zyojYJjHOffEH0!|)eRh@`B8M*DBUdO6X?x%gnSv3QM??_yxJHJ(44YcXwU{wfb?jO
zp594hZw?|`$3hYxM4{g}Fy;1@sesnNLm$CN8uTDNjdRGY8Xx^I+aHTuZyWyQ2h)mG
zuemeJ7|Ha#jGe$psw%ptI*&}MHab}_z*ttI_)?90)s12hKPBuly#ynjmW*BoYL7Ip
z<P0uM;<PZ`j<@hDWW3QC48o=YFk@MRbEsR!W7FTGHL0DZh0t4m0Q;c9d&`P1q53;4
Jc}80$`w!6^e&GNB

diff --git a/kernel/bin/riscv32imac-unknown-xous-elf.a b/kernel/bin/riscv32imac-unknown-xous-elf.a
index c2cb641f57415acc6d5c951146a4308358e55f5e..8e65db07f4a9479c2e3df404d6a87d04a3e9927e 100644
GIT binary patch
delta 2247
zcmaJ?U1(fI7@gUBce71*H+z$q>{iL%-IYm&LN=yJsx1;9#1hd4>`U;$f(?i*)<Q)o
zlnwYtY_*MJ|B~7mf7)u=G_q|K30kb+iw{A>N9k)p#0MYxP=eo?Z)Wduh0bz!&N<(i
z@7tNVGkf8w^=D6PN{<c?4cCT7x6M}ODh`KXEkxt*!CGx(WF!n98y$Xh_Rq~-(-k44
z5MnDmLTnbjqDL3yl0Ogz1^u%eXOK&bmnHe`_qp7dOw7wRZv!Rtd>wd;dd$n{HF}o)
zLR+?}KcfHf7u!WLfr{SQgbuwI^wH$@gxI2gN%rg8$+Z4EIf1_ML~4)USZ-gFaz!7=
zl=S&bKKKsfOiP)c{=NP&GoaTqWAax$kS&$hTv%}Yw;2DUQO^!Yxvm#-rNIOyZyKBZ
z7*EG|MwdE@^|UGMMhd~)Ovs4L{icC=D#p_>-X7zb7|%Igw*~V~u)H(IyJNg3#tSjN
zDaId)@jlCk+>Ez14Zc~CTx_+%W<0I$<c4KVALuBSc{N&MO&5SCHb&kj|L<*<Fr)IO
zZnSdDtIdpgeW#<;OYdGw^F+Y=r|WISa&uLU!xPb>LhwYFF6LhkZrJg8da0%fr}aYq
zT=AM!siQS94VzxLs&@y~!RxGSq0Wu30e{Onj+}d$UojqiDd<b>^ymQ1G;Ri6Ql4%6
z-uY8|eT1aSyF3b5y~B71^!FmHtY-}R9P7Z!dY*^=KI_10hVdlyqY+lt^CI+PqHZD}
z%9^GS_<#oht7DA!LH{tq%6bk$Kh8R^vYt1fpI{wWS<eyZv#cNSsJ^nMw-ES<1Hj6f
zW}s`<ftB?fhyF3^z{+|~LO;nmu(F<c=%-i*R`6i{iwK<N0I;&Ai_p)o4y>$a3Hm(i
zz{+}X2gu8;<9y32jPcgVWyamWUoplJt;?^O;5^DD#wO8cjLqQB8DntuiwO5y9f{<Z
ztRqkLLWKLR9+D(4vi>l2)k_BN5+MCHfLlwRGXY^{@Cjq{BhE86Ggx433V+JjOkhzT
z>U++gdUfwhjUW0Z<c4Xww)RuJTla=lx+1oR)%stgAvqFZrZ`pLPt$`702<n1BB4S2
z<t~TaL>)$Cj>rmagKI9fiv;8zvw^!*cQs2pj>5P#T;VCgZV<fVN!nik+gxl9@z#Xb
zLLqjNhI|`s3==s>j~hc!?5BKG+qQjC@NJS>jnibTIUn`zPXsS%YvFsL5O0!(!noqx
zL~sC*&*fOr3+3KUyd<qvZYT9bx#w|gXKT_!<!Cm6jbS$5&_k>H8g-_nQ@T)5*{!rq
eH)+-nkl4`AR31$H8|arSs<29VZdornSNcDqWyWp*

delta 1273
zcmZ9K&ubG=5XawZk|jyI?rzeCM6_L#bW=(pn>LB5Am$>~Qfm$#deM3i#2-iz#fy*%
z^=H*KPFumo>PeK|Tu<7A6c4$mARa1+di2zTe}Fpk-fkK)Fgu@lGw=I;?E8D{#o@)>
z!Qs*2{e@h~t|gx&JvL3-B$MBqZ5NA0(<~M9cJ0SNw9?BMXN=|185>|R)&mK?4h=pI
zv5s+GaBg(0av1Wxh4212#zA-)=mI;i47O6>X*jE7U`44o+sbJ_zv3L~{K<{iLX19&
z5Pt(%wGU3II^Te4HOn`lsvh6>sjcfvTmBXPseOFQ(RO7yOlmq@Lf;OB4ZjdoXxqXR
z_@)=Q0t;G#hl#5#HPP#JGNy?<+#Ha3swHnCf{%5zrkDrYa=lI8PjxsL?1bNjZfI@Y
z5jYyT+PoeeuV+^De~#1>^_|`k7fCGs80Mm>+*3I;guz&oY!g3|Oux@~F8Mt18f-;-
zosMpm^IMMIvl*`DeT*e<%NAnmrep;JUy@9x<;#+F;uXo=#5Kur;zyGA5QAi)b6>KU
z`#>_yO+94OBBLbZ7KG4(Y$Bo5;tprrak_4PM~;il-IXjBxF=a`ZXW8%N#{>;f`=+t
zyojYJjHOffEH0!|)eRh@`B8M*DBUdO6X?x%gnSv3QM??_yxJHJ(44YcXwU{wfb?jO
zp594hZw?|`$3hYxM4{g}Fy;1@sesnNLm$CN8uTDNjdRGY8Xx^I+aHTuZyWyQ2h)mG
zuemeJ7|Ha#jGe$psw%ptI*&}MHab}_z*ttI_)?90)s12hKPBuly#ynjmW*BoYL7Ip
z<P0uM;<PZ`j<@hDWW3QC48o=YFk@MRbEsR!W7FTGHL0DZh0t4m0Q;c9d&`P1q53;4
Jc}80$`w!6^e&GNB

diff --git a/kernel/bin/riscv32imc-unknown-none-elf.a b/kernel/bin/riscv32imc-unknown-none-elf.a
index c2cb641f57415acc6d5c951146a4308358e55f5e..8e65db07f4a9479c2e3df404d6a87d04a3e9927e 100644
GIT binary patch
delta 2247
zcmaJ?U1(fI7@gUBce71*H+z$q>{iL%-IYm&LN=yJsx1;9#1hd4>`U;$f(?i*)<Q)o
zlnwYtY_*MJ|B~7mf7)u=G_q|K30kb+iw{A>N9k)p#0MYxP=eo?Z)Wduh0bz!&N<(i
z@7tNVGkf8w^=D6PN{<c?4cCT7x6M}ODh`KXEkxt*!CGx(WF!n98y$Xh_Rq~-(-k44
z5MnDmLTnbjqDL3yl0Ogz1^u%eXOK&bmnHe`_qp7dOw7wRZv!Rtd>wd;dd$n{HF}o)
zLR+?}KcfHf7u!WLfr{SQgbuwI^wH$@gxI2gN%rg8$+Z4EIf1_ML~4)USZ-gFaz!7=
zl=S&bKKKsfOiP)c{=NP&GoaTqWAax$kS&$hTv%}Yw;2DUQO^!Yxvm#-rNIOyZyKBZ
z7*EG|MwdE@^|UGMMhd~)Ovs4L{icC=D#p_>-X7zb7|%Igw*~V~u)H(IyJNg3#tSjN
zDaId)@jlCk+>Ez14Zc~CTx_+%W<0I$<c4KVALuBSc{N&MO&5SCHb&kj|L<*<Fr)IO
zZnSdDtIdpgeW#<;OYdGw^F+Y=r|WISa&uLU!xPb>LhwYFF6LhkZrJg8da0%fr}aYq
zT=AM!siQS94VzxLs&@y~!RxGSq0Wu30e{Onj+}d$UojqiDd<b>^ymQ1G;Ri6Ql4%6
z-uY8|eT1aSyF3b5y~B71^!FmHtY-}R9P7Z!dY*^=KI_10hVdlyqY+lt^CI+PqHZD}
z%9^GS_<#oht7DA!LH{tq%6bk$Kh8R^vYt1fpI{wWS<eyZv#cNSsJ^nMw-ES<1Hj6f
zW}s`<ftB?fhyF3^z{+|~LO;nmu(F<c=%-i*R`6i{iwK<N0I;&Ai_p)o4y>$a3Hm(i
zz{+}X2gu8;<9y32jPcgVWyamWUoplJt;?^O;5^DD#wO8cjLqQB8DntuiwO5y9f{<Z
ztRqkLLWKLR9+D(4vi>l2)k_BN5+MCHfLlwRGXY^{@Cjq{BhE86Ggx433V+JjOkhzT
z>U++gdUfwhjUW0Z<c4Xww)RuJTla=lx+1oR)%stgAvqFZrZ`pLPt$`702<n1BB4S2
z<t~TaL>)$Cj>rmagKI9fiv;8zvw^!*cQs2pj>5P#T;VCgZV<fVN!nik+gxl9@z#Xb
zLLqjNhI|`s3==s>j~hc!?5BKG+qQjC@NJS>jnibTIUn`zPXsS%YvFsL5O0!(!noqx
zL~sC*&*fOr3+3KUyd<qvZYT9bx#w|gXKT_!<!Cm6jbS$5&_k>H8g-_nQ@T)5*{!rq
eH)+-nkl4`AR31$H8|arSs<29VZdornSNcDqWyWp*

delta 1273
zcmZ9K&ubG=5XawZk|jyI?rzeCM6_L#bW=(pn>LB5Am$>~Qfm$#deM3i#2-iz#fy*%
z^=H*KPFumo>PeK|Tu<7A6c4$mARa1+di2zTe}Fpk-fkK)Fgu@lGw=I;?E8D{#o@)>
z!Qs*2{e@h~t|gx&JvL3-B$MBqZ5NA0(<~M9cJ0SNw9?BMXN=|185>|R)&mK?4h=pI
zv5s+GaBg(0av1Wxh4212#zA-)=mI;i47O6>X*jE7U`44o+sbJ_zv3L~{K<{iLX19&
z5Pt(%wGU3II^Te4HOn`lsvh6>sjcfvTmBXPseOFQ(RO7yOlmq@Lf;OB4ZjdoXxqXR
z_@)=Q0t;G#hl#5#HPP#JGNy?<+#Ha3swHnCf{%5zrkDrYa=lI8PjxsL?1bNjZfI@Y
z5jYyT+PoeeuV+^De~#1>^_|`k7fCGs80Mm>+*3I;guz&oY!g3|Oux@~F8Mt18f-;-
zosMpm^IMMIvl*`DeT*e<%NAnmrep;JUy@9x<;#+F;uXo=#5Kur;zyGA5QAi)b6>KU
z`#>_yO+94OBBLbZ7KG4(Y$Bo5;tprrak_4PM~;il-IXjBxF=a`ZXW8%N#{>;f`=+t
zyojYJjHOffEH0!|)eRh@`B8M*DBUdO6X?x%gnSv3QM??_yxJHJ(44YcXwU{wfb?jO
zp594hZw?|`$3hYxM4{g}Fy;1@sesnNLm$CN8uTDNjdRGY8Xx^I+aHTuZyWyQ2h)mG
zuemeJ7|Ha#jGe$psw%ptI*&}MHab}_z*ttI_)?90)s12hKPBuly#ynjmW*BoYL7Ip
z<P0uM;<PZ`j<@hDWW3QC48o=YFk@MRbEsR!W7FTGHL0DZh0t4m0Q;c9d&`P1q53;4
Jc}80$`w!6^e&GNB

diff --git a/kernel/bin/riscv64gc-unknown-none-elf.a b/kernel/bin/riscv64gc-unknown-none-elf.a
index 3e38f01244b5d726bf2538c7506fead82643a4bb..9c01444003458eb0f40e59d28ad8821b035fc545 100644
GIT binary patch
delta 2643
zcmaKtU1%It6vywK*-U1ekIrUicP243)3mOwsJqE_KR{g;6f31BdGJ9HO-c<2Vzv07
zKGYQ}EveQf9;>$1Bu%QVtu@MO8c{G(5b;6#q7)z67at0~D2Rw4c+Z`4lS2$nm_28H
z=YRh9%*-V-{nSqfCVSjUsaPr$E7hs~lUqz4MTH2D_;;XCD3{AoG*GIR%2U_#L7^)2
zA=PhPXLS*XEZi)ANaUkb2!F_3aZ<B(ZI<Hy|CX8)*1VK9{B8#@W*<>!7yO*qDmygs
zT0RHYZnsWYP`4k3%PsY`-D*usuj|6*!Mh=HT)5A9T1Bt9=)CAOhdP!l`7O-20XSYL
zzsF2o(bq#>2rqaA_{JNPzi5(6h4O~ZYHIX-sjxYn`dC_73A1h%hSH(zf#LM+2}eW{
zmXm>$aK+ETqpgl~;epn`c7+AQtr-;)6dj5##SIkODRxryD0WfwDP}2#6x9IQzn9`B
zSV-rsoP?29Uo9KKMt_tpS7wSJ<)m#}v_Xfz=f6c|2y>Y(ybaqE@qnJ#f=zI1rbi}K
zmQn2~_{Y!7PP~G@eP2D}graG9B=fa;u6@}+Mo`IKke}+#KeN4Z0n)+FJ)i0K6aUb5
z5h-=K$oO59BfrFWo$)2cUt)X_z6kE@7_no7yJ4dFYjBGtPc+j#2Q%F@s`RVMA?m|W
zgN1z1xR+HAv#Q}a#dz2KOn;K;4M#oq8D;t-Oi#QauwjA~##zHF>u}U_qbHdDRi-x_
z_1tGa(;pR$)ecj@25$5$Yj|x{E(}NgQN|B2{jqg8>Q{Vl{e!Gwk~J8P4cusg>8F_9
zaMW|3V@&@#(<9gSj}6@DIBNjbU^wcz(J7{XgXs-NJ@+}is&9znticqpfg7D&Z4hrV
zz2T_mJ{Ot(Ev7dd^|24V|0ZjAn>84Y4czDw)1P8`!%@$D9Ma%-;zOoyH~S9@7g@oh
z9Qj9#`;33Uc*yv9#(NpRz_=NxfeXyBf>{{<kIXY}7TBuTnRWQKHTsA&=<^=s7*K}?
z`n*s3PXklH$Quf}8h_@_QjVcYIU1d#9E0KL!}a{e-dWMB=Wp%|Cw+INAVfqt@@dA+
zpvY$!=Y!5NZU#dAX~xAJ&piJm>>ao#F~0Ayz0J9SAEigLTqT(ghl>^bVl5ADf@{U@
zZQXIfjEuVh-=s@=!*{~yV30hI?^YcVd^Ol7AB4Ug!G`aMeQBeo9EQ;yp>cigrdW@z
zNp-Gu9Y=@cp_W+HuU*Grv>0rEs1&owI0$rTQ|DTT{o3IiIdo}<mo-}^HUf=OpKNH?
z8|3;MbM0Km72tX)usjF;D&^$7wyV?rj_szk-PLmJ!-vH0?b;zffthlUoFs?sI3!#v
fhnZy}v)H7Lj5?dpR=G`vP_5LGk5@Dnm$BntUK<iO

delta 1449
zcmZuxO=uHA6yDkG=8rT@noV{a`?J^@MWo#XP17`u(NYUVy?7C!wFNI0p*h(el!zdx
zt=jth0jq7%i{eGeL1<52JV>w#A|hxDUOn_wJXznHowaMpgE!wd-+S}kFf+SfE-y^X
zCVc6hboZfD)|%V>sNLbFX_;j9n6j))CS#hZgO-(@TkF!ZDTy1yvB+6bic2xr!&c!p
z8-io<5bLYFmY*>=r!0e}8i@O0T@6A(ZG|Pp10(3;%1P8(;DRUT!zy`n8OoXtMQ;ae
zdP<dx-YXt9Q(3EDmEm33U{yHl*WpLlfKbF>pZP2qvDh~_9GQd<5d;39{tLDuU2KD*
zmCnXj3^t<%B(*pM^@QBYU_Cy<!K<+Ve2<UOWXY!~4Uz<lz8GRaU^}F|QALr0h%p$~
zG~8Jo95plu8Ld#&4c0&r%xHvR<1Kp+ZB05epu6cMdrWI#v#FUqglJ-L><K?7d&mkN
zL0oX@bOL0gFLGuNMZrm55}e?w;Jgm3Bzh~MUClBqr-PMD%T$czVJ)qf^NO98M7Sna
z5O@TqTf8SYK~Qkg?+Z>47M%14f)i+hlRhUnfnoEqM1i~ZgpbXFlMXK3y`dSG?lhKB
zyXDeF1E~YG+corkJiojhF$JYUceZ7T63M90ENAxM=!EWk_lB;!@|_J){Tq%>i%l`1
zz)iskoCc&%Lx1*EWg+{Cg=2QgR~w`#lylwUl|nVw9*)}qr(G1ba=LmPMMjS<@RSY~
z?TA9}8mc{kfkB+sp%>BJwk}FJmlegJPdMc{EryZv;_}Zr*yv3ToJOH$!A@GXeT-Bv
zfKElpoPy_(^MXu;iTqymk~8<4D&^r;;Z45n%p|f}eM((CNqTOBM1AVfclMb^jgG@Y
zciX56R$o$`M~!d8Kl@)>df&C$8lujqs6}n*HSBEr0yX^XN+Rtad{kkhuK*`}-jFnk
cKO8dpe&(USaDc_2R4DkTM2{8v3(@WU1!nWIcmMzZ

diff --git a/kernel/bin/riscv64imac-unknown-none-elf.a b/kernel/bin/riscv64imac-unknown-none-elf.a
index 3e38f01244b5d726bf2538c7506fead82643a4bb..9c01444003458eb0f40e59d28ad8821b035fc545 100644
GIT binary patch
delta 2643
zcmaKtU1%It6vywK*-U1ekIrUicP243)3mOwsJqE_KR{g;6f31BdGJ9HO-c<2Vzv07
zKGYQ}EveQf9;>$1Bu%QVtu@MO8c{G(5b;6#q7)z67at0~D2Rw4c+Z`4lS2$nm_28H
z=YRh9%*-V-{nSqfCVSjUsaPr$E7hs~lUqz4MTH2D_;;XCD3{AoG*GIR%2U_#L7^)2
zA=PhPXLS*XEZi)ANaUkb2!F_3aZ<B(ZI<Hy|CX8)*1VK9{B8#@W*<>!7yO*qDmygs
zT0RHYZnsWYP`4k3%PsY`-D*usuj|6*!Mh=HT)5A9T1Bt9=)CAOhdP!l`7O-20XSYL
zzsF2o(bq#>2rqaA_{JNPzi5(6h4O~ZYHIX-sjxYn`dC_73A1h%hSH(zf#LM+2}eW{
zmXm>$aK+ETqpgl~;epn`c7+AQtr-;)6dj5##SIkODRxryD0WfwDP}2#6x9IQzn9`B
zSV-rsoP?29Uo9KKMt_tpS7wSJ<)m#}v_Xfz=f6c|2y>Y(ybaqE@qnJ#f=zI1rbi}K
zmQn2~_{Y!7PP~G@eP2D}graG9B=fa;u6@}+Mo`IKke}+#KeN4Z0n)+FJ)i0K6aUb5
z5h-=K$oO59BfrFWo$)2cUt)X_z6kE@7_no7yJ4dFYjBGtPc+j#2Q%F@s`RVMA?m|W
zgN1z1xR+HAv#Q}a#dz2KOn;K;4M#oq8D;t-Oi#QauwjA~##zHF>u}U_qbHdDRi-x_
z_1tGa(;pR$)ecj@25$5$Yj|x{E(}NgQN|B2{jqg8>Q{Vl{e!Gwk~J8P4cusg>8F_9
zaMW|3V@&@#(<9gSj}6@DIBNjbU^wcz(J7{XgXs-NJ@+}is&9znticqpfg7D&Z4hrV
zz2T_mJ{Ot(Ev7dd^|24V|0ZjAn>84Y4czDw)1P8`!%@$D9Ma%-;zOoyH~S9@7g@oh
z9Qj9#`;33Uc*yv9#(NpRz_=NxfeXyBf>{{<kIXY}7TBuTnRWQKHTsA&=<^=s7*K}?
z`n*s3PXklH$Quf}8h_@_QjVcYIU1d#9E0KL!}a{e-dWMB=Wp%|Cw+INAVfqt@@dA+
zpvY$!=Y!5NZU#dAX~xAJ&piJm>>ao#F~0Ayz0J9SAEigLTqT(ghl>^bVl5ADf@{U@
zZQXIfjEuVh-=s@=!*{~yV30hI?^YcVd^Ol7AB4Ug!G`aMeQBeo9EQ;yp>cigrdW@z
zNp-Gu9Y=@cp_W+HuU*Grv>0rEs1&owI0$rTQ|DTT{o3IiIdo}<mo-}^HUf=OpKNH?
z8|3;MbM0Km72tX)usjF;D&^$7wyV?rj_szk-PLmJ!-vH0?b;zffthlUoFs?sI3!#v
fhnZy}v)H7Lj5?dpR=G`vP_5LGk5@Dnm$BntUK<iO

delta 1449
zcmZuxO=uHA6yDkG=8rT@noV{a`?J^@MWo#XP17`u(NYUVy?7C!wFNI0p*h(el!zdx
zt=jth0jq7%i{eGeL1<52JV>w#A|hxDUOn_wJXznHowaMpgE!wd-+S}kFf+SfE-y^X
zCVc6hboZfD)|%V>sNLbFX_;j9n6j))CS#hZgO-(@TkF!ZDTy1yvB+6bic2xr!&c!p
z8-io<5bLYFmY*>=r!0e}8i@O0T@6A(ZG|Pp10(3;%1P8(;DRUT!zy`n8OoXtMQ;ae
zdP<dx-YXt9Q(3EDmEm33U{yHl*WpLlfKbF>pZP2qvDh~_9GQd<5d;39{tLDuU2KD*
zmCnXj3^t<%B(*pM^@QBYU_Cy<!K<+Ve2<UOWXY!~4Uz<lz8GRaU^}F|QALr0h%p$~
zG~8Jo95plu8Ld#&4c0&r%xHvR<1Kp+ZB05epu6cMdrWI#v#FUqglJ-L><K?7d&mkN
zL0oX@bOL0gFLGuNMZrm55}e?w;Jgm3Bzh~MUClBqr-PMD%T$czVJ)qf^NO98M7Sna
z5O@TqTf8SYK~Qkg?+Z>47M%14f)i+hlRhUnfnoEqM1i~ZgpbXFlMXK3y`dSG?lhKB
zyXDeF1E~YG+corkJiojhF$JYUceZ7T63M90ENAxM=!EWk_lB;!@|_J){Tq%>i%l`1
zz)iskoCc&%Lx1*EWg+{Cg=2QgR~w`#lylwUl|nVw9*)}qr(G1ba=LmPMMjS<@RSY~
z?TA9}8mc{kfkB+sp%>BJwk}FJmlegJPdMc{EryZv;_}Zr*yv3ToJOH$!A@GXeT-Bv
zfKElpoPy_(^MXu;iTqymk~8<4D&^r;;Z45n%p|f}eM((CNqTOBM1AVfclMb^jgG@Y
zciX56R$o$`M~!d8Kl@)>df&C$8lujqs6}n*HSBEr0yX^XN+Rtad{kkhuK*`}-jFnk
cKO8dpe&(USaDc_2R4DkTM2{8v3(@WU1!nWIcmMzZ

diff --git a/kernel/src/asm.S b/kernel/src/asm.S
index 813d2cfef..755a2f9d5 100644
--- a/kernel/src/asm.S
+++ b/kernel/src/asm.S
@@ -154,6 +154,11 @@ _xous_resume_context:
     move        sp, a0
 
     LOAD        x1, 0*REGBYTES(sp)
+    // Clear any reservations, invalidating any atomic operations
+#ifndef SKIP_MULTICORE
+    sc.w	    zero, x1, 0*REGBYTES(sp)
+#endif
+
     // Skip SP for now
     LOAD        x3, 2*REGBYTES(sp)
     LOAD        x4, 3*REGBYTES(sp)
@@ -206,6 +211,21 @@ _xous_syscall_return_result:
     csrw        sepc, t0
 
     LOAD        x1, 0*REGBYTES(sp)
+    // An atomic operation is broken up into multiple instructions.
+    // A program first issues a `lr` instruction, which basically
+    // raises a flag saying that an atomic operation is now live. It
+    // then issues an `sc` instruction, and if the flag is still held
+    // it succeeds and clears the flag.
+    //
+    // This flag is a bit of state within the processor, and the
+    // RISC-V spec doesn't say how to access it. However, it is only
+    // one bit, and we can clear the bit by performing a dummy `sc`
+    // here. This will cause a failure in any atomic operation in the
+    // program we're switching to.
+#ifndef SKIP_MULTICORE
+    sc.w	    zero, x1, 0*REGBYTES(sp)
+#endif
+
     // Skip SP for now
     LOAD        x3, 2*REGBYTES(sp)
     LOAD        x4, 3*REGBYTES(sp)