Re: [GHC] #15608: Segfault in retainer profiling

#15608: Segfault in retainer profiling -------------------------------------+------------------------------------- Reporter: osa1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Profiling | Version: 8.5 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5134 Wiki Page: | -------------------------------------+------------------------------------- Comment (by osa1): One of the problems is that because of recursive `retainClosure()` calls retainer profiler sometimes fills the C stack. I currently see 14000+ stack frames because of this loop: {{{ #174645 retainClosure (c0=<optimized out>, cp0=cp0@entry=0x4201ecaa20, r0=r0@entry=0x6810bc0 ) at rts/RetainerProfile.c:1598 #174646 0x00000000059b48c7 in retain_small_bitmap (c_child_r=<optimized out>, c=0x4201ecaa20, bitmap=0, size=<optimized out>, p=0x4201ecaa50) at rts/RetainerProfile.c:1140 #174647 retain_PAP_payload (n_args=<optimized out>, payload=0x4201ecaa50, fun=<optimized out>, c_child_r=<optimized out>, pap=0x4201ecaa20) at rts/RetainerProfile.c:1334 #174648 retainClosure (c0=<optimized out>, cp0=cp0@entry=0x4203affe88, r0=r0@entry=0x6810bc0 ) at rts/RetainerProfile.c:1598 }}} I don't understand how retainer profiler works yet. It has a stack, and a maxStack variable, but I don't understand why we sometimes push work to the stack and sometimes recurse, and maxStack seems to be unused. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15608#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler