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4fda7936c5
To debug a deadlock, we really want to know what lock is actually locked, so we can figure out what is using that lock. This PR adds support for this, using trylock to check if every lock on the system is free or in use. Will really need to be run a few times in quick succession to verify that it's not a transient lock and it's actually stuck, but that's not really a big deal. Signed-off-by: Matt Heon <mheon@redhat.com>
48 lines
1.5 KiB
C
48 lines
1.5 KiB
C
#ifndef shm_locks_h_
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#define shm_locks_h_
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#include <pthread.h>
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#include <stdint.h>
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// Magic number to ensure we open the right SHM segment
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#define MAGIC 0x87D1
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// Type for our bitmaps
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typedef uint32_t bitmap_t;
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// bitmap size
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#define BITMAP_SIZE (sizeof(bitmap_t) * 8)
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// Struct to hold a single bitmap and associated locks
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typedef struct lock_group {
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bitmap_t bitmap;
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pthread_mutex_t locks[BITMAP_SIZE];
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} lock_group_t;
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// Struct to hold our SHM locks.
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// Unused is required to be 0 in the current implementation. If we ever make
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// changes to this structure in the future, this will be repurposed as a version
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// field.
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typedef struct shm_struct {
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uint16_t magic;
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uint16_t unused;
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pthread_mutex_t segment_lock;
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uint32_t num_bitmaps;
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uint32_t num_locks;
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lock_group_t locks[];
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} shm_struct_t;
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shm_struct_t *setup_lock_shm(char *path, uint32_t num_locks, int *error_code);
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shm_struct_t *open_lock_shm(char *path, uint32_t num_locks, int *error_code);
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int32_t close_lock_shm(shm_struct_t *shm);
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int64_t allocate_semaphore(shm_struct_t *shm);
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int32_t allocate_given_semaphore(shm_struct_t *shm, uint32_t sem_index);
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int32_t deallocate_semaphore(shm_struct_t *shm, uint32_t sem_index);
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int32_t deallocate_all_semaphores(shm_struct_t *shm);
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int32_t lock_semaphore(shm_struct_t *shm, uint32_t sem_index);
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int32_t unlock_semaphore(shm_struct_t *shm, uint32_t sem_index);
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int64_t available_locks(shm_struct_t *shm);
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int32_t try_lock(shm_struct_t *shm, uint32_t sem_index);
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#endif
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