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dir-hold-afs-bufferlock-across-increment-of-buffer-lockers-to-prevent-newslot-from-walking-on-stuff-20020514

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liberal debugging code and hammering produced a failure where newslot was
actually walking on another call to newslot because the bufferlock was
being dropped before newslot incremented lockers on the buffer it
was allocating, allowing someone else to come along and also think they
could allocate it.

by holding the bufferlock just a little longer we avoid this
This commit is contained in:
Derrick Brashear 2002-05-14 21:21:09 +00:00
parent 50473f885f
commit 0eb68f307a
1 changed files with 5 additions and 5 deletions
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10
src/dir/buffer.c
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@ -132,8 +132,8 @@ char *DRead(fid,page)
if ( tb = phTable[pHash(fid)] ) { /* ASSMT HERE */ if ( tb = phTable[pHash(fid)] ) { /* ASSMT HERE */
if (bufmatch(tb)) { if (bufmatch(tb)) {
ObtainWriteLock(&tb->lock); ObtainWriteLock(&tb->lock);
ReleaseWriteLock(&afs_bufferLock);
tb->lockers++; tb->lockers++;
ReleaseWriteLock(&afs_bufferLock);
tb->accesstime = ++timecounter; tb->accesstime = ++timecounter;
ReleaseWriteLock(&tb->lock); ReleaseWriteLock(&tb->lock);
return tb->data; return tb->data;
@ -144,8 +144,8 @@ char *DRead(fid,page)
if (bufmatch(tb2)) { if (bufmatch(tb2)) {
buf_Front(bufhead,tb,tb2); buf_Front(bufhead,tb,tb2);
ObtainWriteLock(&tb2->lock); ObtainWriteLock(&tb2->lock);
ReleaseWriteLock(&afs_bufferLock);
tb2->lockers++; tb2->lockers++;
ReleaseWriteLock(&afs_bufferLock);
tb2->accesstime = ++timecounter; tb2->accesstime = ++timecounter;
ReleaseWriteLock(&tb2->lock); ReleaseWriteLock(&tb2->lock);
return tb2->data; return tb2->data;
@ -154,8 +154,8 @@ char *DRead(fid,page)
if (bufmatch(tb)) { if (bufmatch(tb)) {
buf_Front(bufhead,tb2,tb); buf_Front(bufhead,tb2,tb);
ObtainWriteLock(&tb->lock); ObtainWriteLock(&tb->lock);
ReleaseWriteLock(&afs_bufferLock);
tb->lockers++; tb->lockers++;
ReleaseWriteLock(&afs_bufferLock);
tb->accesstime = ++timecounter; tb->accesstime = ++timecounter;
ReleaseWriteLock(&tb->lock); ReleaseWriteLock(&tb->lock);
return tb->data; return tb->data;
@ -175,8 +175,8 @@ char *DRead(fid,page)
tb = newslot(fid, page, (tb ? tb : tb2)); tb = newslot(fid, page, (tb ? tb : tb2));
ios++; ios++;
ObtainWriteLock(&tb->lock); ObtainWriteLock(&tb->lock);
ReleaseWriteLock(&afs_bufferLock);
tb->lockers++; tb->lockers++;
ReleaseWriteLock(&afs_bufferLock);
if (ReallyRead(tb->fid,tb->page,tb->data)) { if (ReallyRead(tb->fid,tb->page,tb->data)) {
tb->lockers--; tb->lockers--;
FidZap(tb->fid); /* disaster */ FidZap(tb->fid); /* disaster */
@ -399,8 +399,8 @@ char *DNew (fid,page)
return 0; return 0;
} }
ObtainWriteLock(&tb->lock); ObtainWriteLock(&tb->lock);
ReleaseWriteLock(&afs_bufferLock);
tb->lockers++; tb->lockers++;
ReleaseWriteLock(&afs_bufferLock);
ReleaseWriteLock(&tb->lock); ReleaseWriteLock(&tb->lock);
return tb->data; return tb->data;
} }