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| author | Ben Gamari <bgamari.foss@gmail.com> | 2017-07-20 11:33:51 -0400 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2017-07-20 11:33:52 -0400 |
| commit | bade356f79d44c9f6e8918a89d9ffac7f5608dbf (patch) | |
| tree | d6d6fbd7b0cbbeb1468042d4ad19955805931973 /rts/Apply.cmm | |
| parent | 5469ac86f9cc9e83b93ed34ca13f0a4f58f4a9a6 (diff) | |
| download | haskell-bade356f79d44c9f6e8918a89d9ffac7f5608dbf.tar.gz | |
rts: Claim AP_STACK before adjusting Sp
In the fix to #13615 we introduced some logic to atomically blackhole
AP_STACKs closures upon entry. However, this logic was placed *after* a
stack pointer adjustment. This meant that if someone else beat us to
blackholing the AP_STACK we would suspend the thread with uninitialized
content on the stack. This would then later blow up when threadPaused
attempted to walk the stack, hence #13970.
Silly bug but still cost lots of head-scratching to find.
Thanks to albertov for the great repro.
Fixes #13970. Bug originally introduced by the fix to #13615.
Reviewers: austin, erikd, simonmar
Reviewed By: erikd, simonmar
Subscribers: rwbarton, thomie
GHC Trac Issues: #13970, #13615
Differential Revision: https://phabricator.haskell.org/D3760
Diffstat (limited to 'rts/Apply.cmm')
| -rw-r--r-- | rts/Apply.cmm | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/rts/Apply.cmm b/rts/Apply.cmm index 64f0a9bd54..ffcd0352a1 100644 --- a/rts/Apply.cmm +++ b/rts/Apply.cmm @@ -637,11 +637,6 @@ INFO_TABLE(stg_AP_STACK,/*special layout*/0,0,AP_STACK,"AP_STACK","AP_STACK") * than continuing to evaluate the now-defunct closure. */ STK_CHK_ENTER(WDS(Words) + SIZEOF_StgUpdateFrame + WDS(AP_STACK_SPLIM), R1); - /* ensure there is at least AP_STACK_SPLIM words of headroom available - * after unpacking the AP_STACK. See bug #1466 */ - - PUSH_UPD_FRAME(Sp - SIZEOF_StgUpdateFrame, R1); - Sp = Sp - SIZEOF_StgUpdateFrame - WDS(Words); /* * It is imperative that we blackhole lest we may duplicate computation which @@ -657,6 +652,11 @@ INFO_TABLE(stg_AP_STACK,/*special layout*/0,0,AP_STACK,"AP_STACK","AP_STACK") prim_write_barrier; SET_INFO(ap, __stg_EAGER_BLACKHOLE_info); + /* ensure there is at least AP_STACK_SPLIM words of headroom available + * after unpacking the AP_STACK. See bug #1466 */ + PUSH_UPD_FRAME(Sp - SIZEOF_StgUpdateFrame, R1); + Sp = Sp - SIZEOF_StgUpdateFrame - WDS(Words); + TICK_ENT_AP(); LDV_ENTER(ap); ENTER_CCS_THUNK(ap); |