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fix rare latch corruption in concurrentBufferManager; add some asserts

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Sears Russell 2010-09-23 00:21:04 +00:00
parent 62e7663c27
commit 546bb4c767
1 changed files with 10 additions and 4 deletions
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6
src/stasis/bufferManager/concurrentBufferManager.c
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@ -79,11 +79,15 @@ static int chWriteBackPage_helper(stasis_buffer_manager_t* bm, pageid_t pageid,
if(!trywritelock(p->loadlatch,0)) { if(!trywritelock(p->loadlatch,0)) {
ret = EBUSY; ret = EBUSY;
p->needsFlush = 1; // Not atomic. Oh well. p->needsFlush = 1; // Not atomic. Oh well.
if(p->id != pageid) {
fprintf(stderr, "BUG FIX: %s:%d would have corrupted a latch's state, but did not\n", __FILE__, __LINE__);
} }
} else {
if(p->id != pageid) { // it must have been written back... if(p->id != pageid) { // it must have been written back...
unlock(p->loadlatch); unlock(p->loadlatch);
return 0; return 0;
} }
}
} else { } else {
// Uggh. With the current design, it's possible that the trywritelock will block on the writeback thread. // Uggh. With the current design, it's possible that the trywritelock will block on the writeback thread.
// That leaves us with few options, so we expose two sets of semantics up to the caller. // That leaves us with few options, so we expose two sets of semantics up to the caller.
@ -192,6 +196,7 @@ static inline stasis_buffer_concurrent_hash_tls_t * populateTLS(stasis_buffer_ma
if(succ) { if(succ) {
// The getStaleAndRemove was not atomic with the hashtable remove, which is OK (but we can't trust tmp anymore...) // The getStaleAndRemove was not atomic with the hashtable remove, which is OK (but we can't trust tmp anymore...)
assert(tmp == tls->p); assert(tmp == tls->p);
assert(tmp->queue == 1); // We pinned it, but no one else did...
tmp = 0; tmp = 0;
if(tls->p->id >= 0) { if(tls->p->id >= 0) {
ch->page_handle->write(ch->page_handle, tls->p); ch->page_handle->write(ch->page_handle, tls->p);
@ -199,6 +204,7 @@ static inline stasis_buffer_concurrent_hash_tls_t * populateTLS(stasis_buffer_ma
hashtable_remove_finish(ch->ht, &h); // need to hold bucket lock until page is flushed. Otherwise, another thread could read stale data from the filehandle. hashtable_remove_finish(ch->ht, &h); // need to hold bucket lock until page is flushed. Otherwise, another thread could read stale data from the filehandle.
tls->p->id = INVALID_PAGE; // in case loadPage has a pointer to it, and we did this in race with it; when loadPage reacquires loadlatch, it will notice the discrepancy tls->p->id = INVALID_PAGE; // in case loadPage has a pointer to it, and we did this in race with it; when loadPage reacquires loadlatch, it will notice the discrepancy
assert(!tls->p->dirty); assert(!tls->p->dirty);
assert(tls->p->queue == 1); // The pin status should not change
unlock(tls->p->loadlatch); unlock(tls->p->loadlatch);
break; break;
} else { } else {