Skip to content

Fix shared-memory race #2229

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
drisspg merged 1 commit into from
Feb 4, 2026
Merged

Fix shared-memory race #2229

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion flash_attn/cute/block_sparse_utils.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -705,7 +705,7 @@ def handle_block_sparse_empty_tile_correction_sm100(
scale_row_idx = tidx + stage * m_block_size
sScale[scale_row_idx] = row_sum_value
if const_expr(mLSE is not None or learnable_sink is not None):
sScale[scale_row_idx + m_block_size * 2] = row_max_value
sScale[scale_row_idx + q_stage * m_block_size] = row_max_value
acc_flag = row_sum_value == Float32(0.0) or row_sum_value != row_sum_value
stats[stage] = (row_sum_value, row_max_value, acc_flag)

Expand Down
6 changes: 3 additions & 3 deletions flash_attn/cute/flash_fwd_sm100.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1784,7 +1784,7 @@ def softmax_loop(
sScale[tidx + stage * self.m_block_size] = softmax.row_sum[0]
if const_expr(mLSE is not None or learnable_sink is not None):
sScale[
tidx + stage * self.m_block_size + self.m_block_size * 2
tidx + stage * self.m_block_size + self.q_stage * self.m_block_size
] = softmax.row_max[0]
# if tidx == 0:
# cute.printf("softmax row sum stage %d: %f, row_max = %f\n", stage, softmax.row_sum[0], softmax.row_max[0])
Expand Down Expand Up @@ -1853,7 +1853,7 @@ def softmax_loop(
sScale[tidx + stage * self.m_block_size] = softmax.row_sum[0]
if const_expr(mLSE is not None or learnable_sink is not None):
sScale[
tidx + stage * self.m_block_size + self.m_block_size * 2
tidx + stage * self.m_block_size + self.q_stage * self.m_block_size
] = softmax.row_max[0]
cute.arch.mbarrier_arrive(mbar_ptr + self.mbar_softmax_corr_full_offset + stage)

Expand Down Expand Up @@ -2159,7 +2159,7 @@ def correction_loop(
# scale = tSrScale_t2r[0]
row_sum = sScale[tidx + stage * self.m_block_size]
if const_expr(mLSE is not None or learnable_sink is not None):
row_max = sScale[tidx + stage * self.m_block_size + self.m_block_size * 2]
row_max = sScale[tidx + stage * self.m_block_size + self.q_stage * self.m_block_size]
else:
row_max = None
cute.arch.mbarrier_arrive(mbar_ptr + self.mbar_softmax_corr_empty_offset + stage)
Expand Down