On Tue, 10 Mar 2026 16:09:57 -0400 Steven Rostedt <[email protected]> wrote:
> From: Steven Rostedt <[email protected]> > > For the futex system call trace event for FUTEX_LOCK_PI and > FUTEX_UNLOCK_PI commands, show the TID from the value (which is usually in > hex) as well as translate the flags (DIED and WAITERS). > > pi_mutex_hammer-1098 [000] ..... 121.876928: sys_futex(uaddr: > 0x560f40cc8180 (0x450) tid: 1104, FUTEX_LOCK_PI|FUTEX_PRIVATE_FLAG, val: 0, > timespec: 0x7f2f9d4b1e50 (0.000100000)) > pi_mutex_hammer-1128 [000] ..... 121.877120: sys_futex(uaddr: > 0x560f40cc8180 (0x8000042a) tid: 1066 (WAITERS), > FUTEX_LOCK_PI|FUTEX_PRIVATE_FLAG, val: 0, timespec: 0x7f2f8e493e50 > (0.000100000)) > pi_mutex_hammer-1106 [000] ..... 121.877242: sys_futex(uaddr: > 0x560f40cc8180 (0x80000452) tid: 1106 (WAITERS), > FUTEX_UNLOCK_PI|FUTEX_PRIVATE_FLAG, val: 0) > > This makes it easier to see the hand off of a mutex and who the owner was. > > Signed-off-by: Steven Rostedt (Google) <[email protected]> Looks good to me. Reviewed-by: Masami Hiramatsu (Google) <[email protected]> Thanks! > --- > Changes since v1: > https://lore.kernel.org/all/[email protected]/ > > - Updated to have the print processing in kernel/futex/syscall.c > > kernel/futex/syscalls.c | 26 ++++++++++++++++++++++++-- > 1 file changed, 24 insertions(+), 2 deletions(-) > > diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c > index a46706d6bc6c..24d912d9b20d 100644 > --- a/kernel/futex/syscalls.c > +++ b/kernel/futex/syscalls.c > @@ -211,6 +211,9 @@ void futex_print_syscall(struct seq_buf *s, int nr_args, > unsigned long *args, > unsigned int op, cmd; > bool done = false; > > + op = args[1]; > + cmd = op & FUTEX_CMD_MASK; > + > for (int i = 0; !done && i < nr_args; i++) { > > if (seq_buf_has_overflowed(s)) > @@ -225,11 +228,30 @@ void futex_print_syscall(struct seq_buf *s, int > nr_args, unsigned long *args, > seq_buf_printf(s, " (%u)", val); > else > seq_buf_printf(s, " (0x%x)", val); > + > + switch(cmd) { > + case FUTEX_LOCK_PI: > + case FUTEX_UNLOCK_PI: > + seq_buf_printf(s, " tid: %d", > + val & FUTEX_TID_MASK); > + > + if (!(val & > (FUTEX_OWNER_DIED|FUTEX_WAITERS))) > + break; > + > + seq_buf_puts(s, " ("); > + if (val & FUTEX_WAITERS) > + seq_buf_puts(s, "WAITERS"); > + if (val & FUTEX_OWNER_DIED) { > + if (op & FUTEX_WAITERS) > + seq_buf_putc(s, '|'); > + seq_buf_puts(s, "DIED"); > + } > + seq_buf_putc(s, ')'); > + break; > + } > } > continue; > case 1: > - op = args[i]; > - cmd = op & FUTEX_CMD_MASK; > if (cmd <= FUTEX_LOCK_PI2) > seq_buf_printf(s, ", %s", __futex_cmds[cmd]); > else > -- > 2.51.0 > > -- Masami Hiramatsu (Google) <[email protected]>
