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Avoid need for valgrind suppressions for pg_atomic_init_u64 on some platforms.

Previously we used pg_atomic_write_64_impl insidepg_atomic_init_u64. That works correctly, but on platforms without64bit single copy atomicity it could trigger spurious valgrind errorsabout uninitialized memory, because we use compare_and_swap for atomicwrites on such platforms.I previously suppressed one instance of this problem (6c878ed),but as Tom reports that wasn't enough. As the atomic variable cannotyet be concurrently accessible during initialization, it seems betterto have pg_atomic_init_64_impl set the value directly.Change pg_atomic_init_u32_impl for symmetry.Reported-By: Tom LaneAuthor: Andres FreundDiscussion:https://postgr.es/m/1714601.1591503815@sss.pgh.pa.usBackpatch: 9.5-

1 parentc2e71cb commit47c7187Copy full SHA for 47c7187

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src
- include/port/atomics
  - generic.h
- tools
  - valgrind.supp

2 files changed

-16

lines changed

`‎src/include/port/atomics/generic.h`

Lines changed: 2 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -160,7 +160,7 @@ pg_atomic_clear_flag_impl(volatile pg_atomic_flag *ptr)`
`160`	`160`	`staticinlinevoid`
`161`	`161`	`pg_atomic_init_u32_impl(volatilepg_atomic_uint32*ptr,uint32val_)`
`162`	`162`	`{`
`163`		`-pg_atomic_write_u32_impl(ptr,val_);`
	`163`	`+ptr->value=val_;`
`164`	`164`	`}`
`165`	`165`	`#endif`
`166`	`166`
`@@ -330,7 +330,7 @@ pg_atomic_read_u64_impl(volatile pg_atomic_uint64 *ptr)`
`330`	`330`	`staticinlinevoid`
`331`	`331`	`pg_atomic_init_u64_impl(volatilepg_atomic_uint64*ptr,uint64val_)`
`332`	`332`	`{`
`333`		`-pg_atomic_write_u64_impl(ptr,val_);`
	`333`	`+ptr->value=val_;`
`334`	`334`	`}`
`335`	`335`	`#endif`
`336`	`336`

`‎src/tools/valgrind.supp`

Lines changed: 0 additions & 14 deletions

Original file line number	Diff line number	Diff line change
`@@ -134,20 +134,6 @@`
`134`	`134`	`fun:IsBinaryCoercible`
`135`	`135`	`}`
`136`	`136`
`137`		`-# Atomic writes to 64bit atomic vars uses compare/exchange to`
`138`		`-# guarantee atomic writes of 64bit variables. pg_atomic_write is used`
`139`		`-# during initialization of the atomic variable; that leads to an`
`140`		`-# initial read of the old, undefined, memory value. But that's just to`
`141`		`-# make sure the swap works correctly.`
`142`		`-{`
`143`		`-uninitialized_atomic_init_u64`
`144`		`-Memcheck:Cond`
`145`		`-fun:pg_atomic_exchange_u64_impl`
`146`		`-fun:pg_atomic_write_u64_impl`
`147`		`-fun:pg_atomic_init_u64_impl`
`148`		`-}`
`149`		`-`
`150`		`-`
`151`	`137`	`# Python's allocator does some low-level tricks for efficiency. Those`
`152`	`138`	`# can be disabled for better instrumentation; but few people testing`
`153`	`139`	`# postgres will have such a build of python. So add broad`

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Commit47c7187

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2 files changed

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`‎src/include/port/atomics/generic.h`

`‎src/tools/valgrind.supp`

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