Currently the spu coredump code triggers an RCU warning: ============================= WARNING: suspicious RCU usage 5.7.0-rc3-01755-g7cd49f0b7ec7 #1 Not tainted ----------------------------- include/linux/fdtable.h:95 suspicious rcu_dereference_check() usage!
other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by spu-coredump/1343: #0: c0000007fa22f430 (sb_writers#2){.+.+}-{0:0}, at: .do_coredump+0x1010/0x13c8 stack backtrace: CPU: 0 PID: 1343 Comm: spu-coredump Not tainted 5.7.0-rc3-01755-g7cd49f0b7ec7 #1 Call Trace: .dump_stack+0xec/0x15c (unreliable) .lockdep_rcu_suspicious+0x120/0x144 .coredump_next_context+0x148/0x158 .spufs_coredump_extra_notes_size+0x54/0x190 .elf_coredump_extra_notes_size+0x34/0x50 .elf_core_dump+0xe48/0x19d0 .do_coredump+0xe50/0x13c8 .get_signal+0x864/0xd88 .do_notify_resume+0x158/0x3c8 .interrupt_exit_user_prepare+0x19c/0x208 interrupt_return+0x14/0x1c0 This comes from fcheck_files() via fcheck(). It's pretty clearly documented that fcheck() must be wrapped with rcu_read_lock(), so fix it. Signed-off-by: Michael Ellerman <m...@ellerman.id.au> --- arch/powerpc/platforms/cell/spufs/coredump.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/platforms/cell/spufs/coredump.c b/arch/powerpc/platforms/cell/spufs/coredump.c index 8b3296b62f65..0fc52cbaa552 100644 --- a/arch/powerpc/platforms/cell/spufs/coredump.c +++ b/arch/powerpc/platforms/cell/spufs/coredump.c @@ -82,13 +82,19 @@ static int match_context(const void *v, struct file *file, unsigned fd) */ static struct spu_context *coredump_next_context(int *fd) { + struct spu_context *ctx; struct file *file; int n = iterate_fd(current->files, *fd, match_context, NULL); if (!n) return NULL; *fd = n - 1; + + rcu_read_lock(); file = fcheck(*fd); - return SPUFS_I(file_inode(file))->i_ctx; + ctx = SPUFS_I(file_inode(file))->i_ctx; + rcu_read_unlock(); + + return ctx; } int spufs_coredump_extra_notes_size(void) -- 2.25.1