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ipc/sem.c: increase SEMMSL, SEMMNI, SEMOPM
a) SysV can be abused to allocate locked kernel memory. For most systems, a small limit doesn't make sense, see the discussion with regards to SHMMAX. Therefore: Increase the sysv sem limits so that all known applications will work with these defaults. b) With regards to the maximum supported: Some of the specified hard limits are not correct anymore, therefore the patch updates the documentation. - SEMMNI must stay below IPCMNI, which is 32768. As for SHMMAX: Stay a bit below this limit. - SEMMSL was limited to 8k, to ensure that the kmalloc for the kernel array was limited to 16 kB (order=2) This doesn't apply anymore: - the allocation size isn't sizeof(short)*nsems anymore. - ipc_alloc falls back to vmalloc - SEMOPM should stay below 1000, to limit the kmalloc in semtimedop() to an order=1 allocation. Therefore: Leave it at 500 (order=0 allocation). Note: If an administrator must limit the memory allocations, then he can set the values as necessary. Or he can disable sysv entirely (as e.g. done by Android). Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Acked-by: Rafael Aquini <aquini@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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1 changed files with 15 additions and 3 deletions
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@ -63,10 +63,22 @@ struct seminfo {
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int semaem;
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};
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#define SEMMNI 128 /* <= IPCMNI max # of semaphore identifiers */
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#define SEMMSL 250 /* <= 8 000 max num of semaphores per id */
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/*
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* SEMMNI, SEMMSL and SEMMNS are default values which can be
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* modified by sysctl.
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* The values has been chosen to be larger than necessary for any
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* known configuration.
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*
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* SEMOPM should not be increased beyond 1000, otherwise there is the
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* risk that semop()/semtimedop() fails due to kernel memory fragmentation when
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* allocating the sop array.
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*/
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#define SEMMNI 32000 /* <= IPCMNI max # of semaphore identifiers */
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#define SEMMSL 32000 /* <= INT_MAX max num of semaphores per id */
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#define SEMMNS (SEMMNI*SEMMSL) /* <= INT_MAX max # of semaphores in system */
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#define SEMOPM 32 /* <= 1 000 max num of ops per semop call */
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#define SEMOPM 500 /* <= 1 000 max num of ops per semop call */
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#define SEMVMX 32767 /* <= 32767 semaphore maximum value */
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#define SEMAEM SEMVMX /* adjust on exit max value */
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