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Allow DSM allocation to be interrupted.
Chris Travers reported that the startup process can repeatedly try to cancel a backend that is in a posix_fallocate()/EINTR loop and cause it to loop forever. Teach the retry loop to give up if an interrupt is pending. Don't actually check for interrupts in that loop though, because a non-local exit would skip some clean-up code in the caller. Back-patch to 9.4 where DSM was added (and posix_fallocate() was later back-patched). Author: Chris Travers Reviewed-by: Ildar Musin, Murat Kabilov, Oleksii Kliukin Tested-by: Oleksii Kliukin Discussion: https://postgr.es/m/CAN-RpxB-oeZve_J3SM_6%3DHXPmvEG%3DHX%2B9V9pi8g2YR7YW0rBBg%40mail.gmail.com
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@ -47,6 +47,7 @@
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*/
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#include "postgres.h"
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#include "miscadmin.h"
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#include <fcntl.h>
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#include <string.h>
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@ -332,6 +333,14 @@ dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size,
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shm_unlink(name);
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errno = save_errno;
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/*
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* If we received a query cancel or termination signal, we will have
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* EINTR set here. If the caller said that errors are OK here, check
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* for interrupts immediately.
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*/
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if (errno == EINTR && elevel >= ERROR)
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CHECK_FOR_INTERRUPTS();
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ereport(elevel,
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(errcode_for_dynamic_shared_memory(),
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errmsg("could not resize shared memory segment \"%s\" to %zu bytes: %m",
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@ -421,11 +430,15 @@ dsm_impl_posix_resize(int fd, off_t size)
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#if defined(HAVE_POSIX_FALLOCATE) && defined(__linux__)
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if (rc == 0)
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{
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/* We may get interrupted, if so just retry. */
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/*
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* We may get interrupted. If so, just retry unless there is an
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* interrupt pending. This avoids the possibility of looping forever
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* if another backend is repeatedly trying to interrupt us.
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*/
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do
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{
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rc = posix_fallocate(fd, 0, size);
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} while (rc == EINTR);
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} while (rc == EINTR && !(ProcDiePending || QueryCancelPending));
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/*
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* The caller expects errno to be set, but posix_fallocate() doesn't
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