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Shared memory descriptors are not closed after PHP program execution is complete. #17245

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CoderAImen opened this issue Dec 23, 2024 · 4 comments · May be fixed by #17273
Open

Shared memory descriptors are not closed after PHP program execution is complete. #17245

CoderAImen opened this issue Dec 23, 2024 · 4 comments · May be fixed by #17273
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@cmb69
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Bug Category: TSRM OS: Windows Status: Needs Triage

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@CoderAImen
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Description

Extension SHMOP.

shm_id = shmop_open($r, "c", 0644,1024000); ?>

When the web server is running for a long time, the number of open descriptors reaches 15 million or more. As a result, the web server complains about the lack of resources.

Shared memory descriptors are not closed after PHP program execution is complete.

Apache 2.4.62 PHP 8.4(php8apache2_4.dll) Windows 11.

PHP Version

PHP 8.4

Operating System

Windows 11
@cmb69
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cmb69 commented Dec 23, 2024

php-src/TSRM/tsrm_win32.c

Lines 751 to 754 in bf5e6c5

if (shm->descriptor->shm_nattch <= 0) {
ret = UnmapViewOfFile(shm->descriptor) ? 0 : -1;
shm->descriptor = NULL;
}

It seems to me that we need to unmap unconditionally, but should close the handle if the refcount drops to zero (the latter might not be necessary).

@cmb69 cmb69 self-assigned this Dec 23, 2024
@CoderAImen
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php-src/TSRM/tsrm_win32.c

Lines 751 to 754 in bf5e6c5

if (shm->descriptor->shm_nattch <= 0) {
ret = UnmapViewOfFile(shm->descriptor) ? 0 : -1;
shm->descriptor = NULL;
}

It seems to me that we need to unmap unconditionally, but should close the handle if the refcount drops to zero (the latter might not be necessary).

php-src/TSRM/tsrm_win32.c

Lines 686 to 691 in bf5e6c5

shm = shm_get(key, NULL);
if (!shm) {
CloseHandle(shm_handle);
return -1;
}
shm->segment = shm_handle;

At this point the open Handle is lost, since no one closed shm->segment.

@dktapps
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dktapps commented Dec 24, 2024

Is this a problem outside of shmop? It might explain some strange "out of resources" user issues I've seen in my applications over the years. Basically, is OPcache also affected by this?

@cmb69
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cmb69 commented Dec 24, 2024

OPcache should not be affected, but the underlying emulation of POSIX shared memory primitives is in tsrm_win32.c, and can be used by other clients than ext/shmop (for instance, it is also used by ext/sysvshm).

@CoderAImen CoderAImen linked a pull request Dec 26, 2024 that will close this issue
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@devnexen devnexen linked a pull request Dec 26, 2024 that will close this issue
Fixed work with Shared Memory on Windows. #17273
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Bug Category: TSRM OS: Windows Status: Needs Triage
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Fixed work with Shared Memory on Windows. CoderAImen/php-src
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@cmb69 @dktapps @CoderAImen