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MDEV-36760 log_t::append_prepare_wait(): Bogus assertion on write_lsn

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log_t::append_prepare_wait(): Do not attempt to read log_sys.write_lsn
because it is not protected by log_sys.latch but by write_lock, which
we cannot hold here. The assertion could fail if log_t::write_buf()
is executing concurrently, and it has not yet executed log_write_buf()
or updated log_sys.write_lsn.

Fixes up commit acd071f599 (MDEV-21923)
This commit is contained in:
Marko Mäkelä
2025-05-08 11:18:16 +03:00
parent a7278a3024
commit 0c18e5a292
1 changed files with 7 additions and 8 deletions
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15
storage/innobase/mtr/mtr0mtr.cc
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@ -916,17 +916,16 @@ ATTRIBUTE_COLD void log_t::append_prepare_wait(bool late, bool ex) noexcept
{
got_ex:
const uint64_t l= write_lsn_offset.load(std::memory_order_relaxed);
const lsn_t lsn{base_lsn.load(std::memory_order_relaxed)};
ut_d(lsn_t ll= lsn + (l & (WRITE_BACKOFF - 1)));
ut_ad(is_mmap()
? ll - get_flushed_lsn(std::memory_order_relaxed) < capacity()
: ll - write_lsn - ((write_size - 1) & (write_lsn - first_lsn)) <
buf_size);
const lsn_t lsn= base_lsn.load(std::memory_order_relaxed) +
(l & (WRITE_BACKOFF - 1));
waits++;
#ifdef HAVE_PMEM
const bool is_pmem{is_mmap()};
if (is_pmem)
persist(lsn + (l & (WRITE_BACKOFF - 1)));
{
ut_ad(lsn - get_flushed_lsn(std::memory_order_relaxed) < capacity());
persist(lsn);
}
#endif
latch.wr_unlock();
/* write_buf() or persist() will clear the WRITE_BACKOFF flag,
@ -934,7 +933,7 @@ ATTRIBUTE_COLD void log_t::append_prepare_wait(bool late, bool ex) noexcept
#ifdef HAVE_PMEM
if (!is_pmem)
#endif
log_write_up_to(lsn + (l & (WRITE_BACKOFF - 1)), false);
log_write_up_to(lsn, false);
if (ex)
{
latch.wr_lock(SRW_LOCK_CALL);