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]> --- 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
