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runtime: merge workarounds to false deadlocks #40518

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prattmic opened this issue Jul 31, 2020 · 4 comments
Open

runtime: merge workarounds to false deadlocks #40518

prattmic opened this issue Jul 31, 2020 · 4 comments
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsFix The path to resolution is known, but the work has not been done.
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Backlog

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@prattmic
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In #40368, I avoided false deadlocks from startm in sysmon by reserving M ids in advance to make it look like the new M is already running to checkdead.

Later, I discovered that @dvyukov fixed a nearly identical issue in #6070 by temporarily decrementing the number of idle locked M's, to make checkdead see an extra M. Slightly different approach, but same end result.

We should merge these two approaches back to one just to keep things simpler and easier to understand.

cc @aclements @mknyszek @ianlancetaylor
@prattmic prattmic added the NeedsFix The path to resolution is known, but the work has not been done. label Jul 31, 2020
@prattmic prattmic added this to the Go1.16 milestone Jul 31, 2020
@prattmic prattmic self-assigned this Jul 31, 2020
@prattmic prattmic mentioned this issue Jul 31, 2020
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@aclements
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With your change to startm to reserve an ID while holding sched.lock, is the logic in sysmon even necessary?

@prattmic
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prattmic commented Jul 31, 2020 •
edited

I'm almost certain that the incidlelocked logic in sysmon is unnecessary after my change. There is similar logic in retake that I'll need to look at more closely.

@aclements
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Bumping to 1.17, but @prattmic, please bump to Backlog if you don't plan on working on this in 1.17.

@aclements aclements modified the milestones: Go1.16, Go1.17 Dec 8, 2020
@ianlancetaylor
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@prattmic Is anything going to happen in 1.17? If not, we should change the milestone to Backlog. Thanks.

@prattmic prattmic modified the milestones: Go1.17, Backlog May 3, 2021
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Jul 7, 2022
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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsFix The path to resolution is known, but the work has not been done.
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Go Compiler / Runtime
Status: Todo
Milestone
Backlog
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@prattmic @aclements @ianlancetaylor @gopherbot