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Fix double-release of spinlock

Commit9d9b9d4 added spinlocks to protect the fields in ProcSignalflags, but in EmitProcSignalBarrier(), the spinlock was releasedtwice. With most spinlock implementations, releasing a lock that's notheld is not easy to notice, because most of the time it does nothing,but if the spinlock was concurrently acquired by another process, itcould lead to more serious issues. Fortunately, with the--disable-spinlocks emulation implementation, it caused more visiblefailures.In the passing, fix a type in comment and add an assertion that theprocNumber passed to SendProcSignal looks valid.Discussion:https://www.postgresql.org/message-id/b8ce284c-18a2-4a79-afd3-1991a2e7d246@iki.fi

1 parent8bda213 commit0393f54Copy full SHA for 0393f54

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src/backend/storage/ipc
- procsignal.c

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`‎src/backend/storage/ipc/procsignal.c‎`

Lines changed: 4 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -284,6 +284,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, ProcNumber procNumber)`
`284`	`284`
`285`	`285`	`if (procNumber!=INVALID_PROC_NUMBER)`
`286`	`286`	`{`
	`287`	`+Assert(procNumber<NumProcSignalSlots);`
`287`	`288`	`slot=&ProcSignal->psh_slot[procNumber];`
`288`	`289`
`289`	`290`	`SpinLockAcquire(&slot->pss_mutex);`
`@@ -300,7 +301,7 @@ SendProcSignal(pid_t pid, ProcSignalReason reason, ProcNumber procNumber)`
`300`	`301`	`else`
`301`	`302`	`{`
`302`	`303`	`/*`
`303`		`- *Pronumber not provided, so search the array using pid. We search`
	`304`	`+ *procNumber not provided, so search the array using pid. We search`
`304`	`305`	`* the array back to front so as to reduce search overhead. Passing`
`305`	`306`	`* INVALID_PROC_NUMBER means that the target is most likely an`
`306`	`307`	`* auxiliary process, which will have a slot near the end of the`
`@@ -404,7 +405,8 @@ EmitProcSignalBarrier(ProcSignalBarrierType type)`
`404`	`405`	`SpinLockRelease(&slot->pss_mutex);`
`405`	`406`	`kill(pid,SIGUSR1);`
`406`	`407`	`}`
`407`		`-SpinLockRelease(&slot->pss_mutex);`
	`408`	`+else`
	`409`	`+SpinLockRelease(&slot->pss_mutex);`
`408`	`410`	`}`
`409`	`411`	`}`
`410`	`412`

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Commit0393f54

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`‎src/backend/storage/ipc/procsignal.c‎`

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